Created by Matt Garvey
Original version 2009, revised and expanded 2024

Introduction

How does one identify an episode of television? There are usually several options, and the answer depends on who is identifying it, for whom, and in what context. For example, is it a viewer, creator, broadcaster? Is it to create a schedule, discuss a plot, etc.?

Most episodes of scripted TV have official titles. Those titles often appeared at episodes' beginnings, far more commonly in the early days of TV, and they began falling out of use long before online listings and other electronic resources made it easy to find a given one. Some printed guides had them, but for decades many viewers would never know episode titles of their favorite shows, let alone that titles existed. (Look at a list of Friends episodes to see one result of this uncertainty.) Titles may vary (and lose puns!) in translation, making them hard to rely on or understand. And they're often cumbersome for brevity and official use among broadcasters.

Season-episode numbers are short and sweet, but they can be ambiguous for a variety of reasons. Are these in production or air order, or maybe a special DVD order? Does a double-length two-part episode count as one or two? Did the episodes air in a different order in another country, or were some skipped entirely? Are the season boundaries defined the same way by everyone? Sometimes the first episode broadcast is advertised as a special or preview, with the second episode being the "series premiere", so which is the "first episode"? And for series in progress, particularly among the production staff making the darn thing, how can air order be known for certain? (Also, is episode "one-oh-two", for example, the second episode of season 1, or the 102nd episode?)

Production codes lend both certainty and brevity to episode identification. Most if not all scripted TV shows have some code system to keep things straight, from script writing through production and broadcast. The system may just be the series name and season-episode number, run together like a hotel room number (101, 203, 522). Or it may be a more elaborate system shared by many shows at a single production company, with no shows' episode codes overlapping, at least within a reasonable time frame, say a decade or so. These are primarily useful for the production and broadcast side, but if the codes are made available, say by putting them onscreen for viewers, they can be useful to everyone. Official but offscreen codes offer little advantage and can still lead to ambiguity.

The Simpsons is one of the shows that use distinctive production codes (unique-ish within 20th Century Fox Television/20th Television) and include the codes in the credits for all to see. The mass appeal and longevity of the show combined with the vocal group of nerds among its fans have made the use of production codes as a primary identifier (or shorthand, especially to those with good memory) a stamp of Simpsons nerddom; few series seem to inspire the rabid latching-on to codes by fans for quick episode reference, The Simpsons and Star Trek (whose numbers aren't even shown) being primary in my mind. The show itself has recognized this quirk and had fun with it, often including production codes in DVD commentaries (and all DVD booklets since season 2), on occasional merchandise, and in jokes in episodes.

Additional advantages to fan use of these codes include incredible brevity in lists and grids, and the ability to view Simpsons trends, evolution, and oddities by production order rather than air order. (For example, observing from 2F16 and 2F20 that "Who Shot Mr. Burns?" was not originally planned as two parts.) Episodes on undated recordings can be identified easily. Greater familiarity gives codes some meaning at just a glance. But they're not very self-explanatory, and can be very confusing or daunting to the uninitiated; any single episode's code can be found and used, but why does 4F02 come from season 8, while 7F08 is from season 2, and where did CABF14 get so many letters? When a similar set of letters and numbers shows up in another 20th Century Fox show, how is it related?

Fortunately, it's not hard; it's fun! This document aims to demystify it all for you, with Simpsons-specific information at the top and then the broader system(s) it fits into. So join me, won't you?

Table of contents

The Simpsons production codes

• Quick reference
• Appearance
• What the codes mean
• Oddities and special numbers
• References in the show

The Simpsons production codes

Quick reference: codes by production season

If you just want to see what a code means, or refresh your memory, or look for a trend all on your own, start here. These are production seasons; not only are episodes often broadcast slightly out of order, most seasons leave a few episodes for the next air season (or two!). A full list of episodes in air order is here, but in short:

Season 1:    7G01-13
Season 2:    7F01-24
Season 3:    8F01-24
Season 4:    9F01-22
Season 5:    1F01-22
Season 6:    2F01-22, 2F31-33
Season 7:    3F01-24, 3F31, 3G01-04
Season 8:    4F01-24
Season 9:    5F01-24
Season 10: AABF01-23
Season 11: BABF01-22
Season 12: CABF01-22
Season 13: DABF01-22
Season 14: EABF01-22
Season 15: FABF01-23
Season 16: GABF01-22
Season 17: HABF01-22
Season 18: JABF01-22
Season 19: KABF01-22
Season 20: LABF01-20
Season 21: MABF01-22
Season 22: NABF01-22
Season 23: PABF01-22
Season 24: RABF01-22
Season 25: SABF01-22
Season 26: TABF01-22
Season 27: VABF01-22
Season 28: WABF01-22
Season 29: XABF01-22
Season 30: YABF01-22
Season 31: ZABF01-22
Season 32: QABF01-22
Season 33: UABF01-22
Season 34: OABF01-22
Season 35 and beyond: 35ABF01, etc.

The Simpsons Movie, of course, has no television production code. It's just "the movie". (Its serial MPAA certificate number is 43622, for what it's worth.)

Some oddities are already evident, but they will be explained.

Appearance

These codes always appear on the copyright page in the credits. Format and placement (quotes mine):

• 7G08 (1st episode broadcast) as a simple "7G08" in the last line of some midscreen legalese, after the period, a fittingly 80s style for the only episode broadcast in the 80s.
• 7G02, 7G03, 7G04 as "THE SIMPSONS EPISODE NO. 7G02" etc. on a line of its own above the copyright notice.
• From 7G05 (5th aired) to OABF13 (air season 34 finale), "THE SIMPSONS EPISODE #7G05" (same place above copyright) and so on. (The lone double-length episode in season 28 uses "THE SIMPSONS EPISODE #WABF04 & #WABF05" when not split into halves.) This style helps make the existence of the code less cryptic, and it was used by a handful of other shows (most others being animated series?). It predominated for over 700 episodes with premiere dates ranging from 2/4/90 to 5/21/23, including the late-premiering 7G01.
• Since the beginning of air season 35 (10/1/23), with some company-wide rearrangement of the copyright screen, it's now simply "Production #OABF18" and so on (around the same place on the screen, under copyright and all-rights-reserved). This is a more common style in the 21st century, and other shows transitioned around the same time too. But it's a little more boring and less customized.

What the codes mean

Simpsons production codes can be difficult to follow in part because they span three code traditions from 20th Century Fox Television. Further complications arise from extra twists (numerical discontinuity, the 3Gs, etc.). In short, all Simpsons episode codes consist of a prefix designating the production season and two digits indicating the episode number within that season. All prefixes except 7G and 3G can be further broken down into a year/season signifier and a characteristic letter or group of letters marking it as The Simpsons (F or ABF).

Season 1 (7G): tail end of the 80s. As illustrated below, the 20thCFT system of code prefixes at this time, while more orderly than its predecessors, was still mostly a random collection of digit-letter combinations. For example, The Tracey Ullman Show used 4W and 5W for the episodes that spawned our favorite family. Its next season was 7W, possibly because there was a gap in time, but the show had no claim to the letter W, or to a number near 4 or 5, even if renewed shows tended to get similar codes for new seasons and a lot of 5s-7s were in use at the time. The point is that "7G" cannot be broken down further. It simply means "season 1 of The Simpsons", which was 1989-90. Had this system continued, season 2 might have been 8G, or 8F, or 7L.
Looking at episode production codes in season 1 also clears up some confusion about what the "first" episode is, or at least eliminates one common nominee. 7G01 is the first episode in production order; originally the show was meant for a fall 89 debut but the animation coming back was not good, and a lot had to be redone. This episode needed the most work and wound up airing last of the 13 7Gs. The whole season slipped, and 7G08, suitably numbered to land at about Christmas, and ready in time, was the first episode to air, followed by 7G02 four weeks later and so on, now with fixed animation. But 7G08 was branded as "The Simpsons Christmas Special" onscreen, and the series was advertised as beginning in January 1990, creating the impression that a one-off special led to the creation of a whole series and 7G02 was the first real episode, with 7G08 just grandfathered in. This is obviously untrue. (It's also incorrect to call any of these episodes a pilot. This is discussed below.)

Season 2-9 (7F-9F, 1F-5F): the more orderly 90s. Before the season 2 codes were assigned, 20thCFT instituted a more rigorous system. Prefixes were still digit-letter combinations, but now each digit would refer to the calendar season (starting with 7 for 90-91, wrapping from 9 to 1, etc., ending with 5 for 97-98), and each letter would consistently represent one show (F = Simpsons). As shows were cancelled, their letters could be recycled, but within a show's lifetime the letter would be its own, and the digits applied to all series. It's a little confusing to go from 7G to 7F, but 7G couldn't be reused, and at least two other shows had similar 7-7 transitions; had this system begun a year earlier, perhaps season 1 would be 6F (or 6G, then 7G for season 2, etc.), and had it continued for one more year instead, season 10 would almost certainly be 6F. As it is, there are no 6F episodes, and of course no 0F either.

Season 7 special episodes (3G). Four extra episodes were produced by earlier showrunners Al Jean and Mike Reiss, bearing season 7-style codes, though they did not air until season 8 and 9. In this case, 3 means the calendar year matching season 7, and G seems to be used for its proximity to F and/or precedent of 7G. More on these in numbering oddities below.

Season 10-31 (AABF-ZABF): 21st Century Fox. Around early 1998, 20thCFT switched to yet another system, and I like to think the longevity of The Simpsons played some part in that. (After all, it could recycle characteristic letters for a while, trying to avoid duplicates, but if Simpsons season 10 were 6F, season 11 couldn't be 7F again!) Now, prefixes would be 4 characters instead of 2: the first to refer to the season number of the series (not the absolute calendar year), then three letters to identify the series, drawn on a sequence like license plates. The Simpsons is "ABF", and that means what "F" used to before. It even kept the "F" (and not all series got that courtesy!).
However, since the switch was made for season 10 (for some official season 9 stuff, see oddities below), letters continued the numerical sequence, thus season 10 is A+ABF+01=AABF01 and so on. 10 is A, 11 is B, etc. In isolation, it appeared that things had gone 4, 5, AAB, BAB..., and it was a little confusing at first. Since ABF is its own atomic unit and does not change, reading these codes aloud is best done with emphasis on the first letter, a quick ABF without stress, and then the episode number itself with some emphasis; pronunciations like "DAB-F06" (as heard in episode DABF15) aren't really right.
The letters I, O, Q, and U are skipped in the season-number lettering to avoid confusion, or they were at first. The alphabet is already a bit of a stopgap, but who could use it all up by getting past 31 seasons?

Season 32-34 (QABF, UABF, OABF): exhausting the alphabet (almost). What comes after the letter Z? I pondered many options, but either the producers or someone at 20th Television (not 20thCFT for long: coincidentally, the Disney/Fox deal happened around this time!) settled on returning to the forbidden letters. This already makes things confusing for sorting, but even these letters are used out of order: QUO. And the letter I remained unused. (At least either way there's a handy mnemonic device.) The reason for all of this is unclear, but my guess is that the show was not expected to continue long enough to break this patch too; renewals occurred for pairs of seasons and codes seem to have been allocated at that time, a theory that does more to explain the abandonment of I than the order used here, since it would result in Z and Q for one renewal, then U and O for the next. O and I were the least desirable letters for their obvious resemblance to 0 and 1; perhaps U was still promoted just in case a sudden end spared O. On the plus side, with high definition, better credits presentation (for The Simpsons anyway) on Fox and in syndication in recent years, etc., these tricky letters are easier to make out than they used to be.

Season 35 and up (35ABF, etc.): back to numbers. After all that messing about with leftover letters, and in fact using the alphabet in the first place, it just went to a 2-digit year, and here it seems destined to stay. (Was I skipped because it was completely off limits, or because the February 2023 renewal for seasons 35 and 36 would otherwise have created I and 36?) At least this, for the first time in Simpsons history, creates a pretty obvious code.
In retrospect, though, it probably would have been wiser to go from ZABF to 32ABF. But we're stuck with these unsortable codes now (eat your heart out, 9F-1F!). Some might say even 10ABF to 31ABF would have been better! (Having often dropped the ABF in shorthand notes, for episode designations like P07, and now being faced with the production/air order ambiguity of, e.g., 3501, I do think the core letter system has a certain advantage. Wherever letters are used, purely numeric interpretation is impossible.)

Now that The Simpsons has blazed the trail for other long-running shows (which transitioned uniformly from 9 to A), it will be interesting to see whether they match the new wrinkles. As I write this update in summer 2024, Family Guy is nearing the end of its NACX production season. Will it add any of the QUO letters in its alphabetical sequence? Will ZACX lead to, say, 31ACX (as discussed below, it skipped G!), or will it also grasp at straws for a few more years with unused letters? Time will tell. My hunch is NACX will lead to PACX, Q and U may get used in order, and ZACX will go to a 2-digit number + ACX.

It's funny to see how the show has not only spanned 3 code styles, but stretched two of them to their limits, arguably breaking the last one, or at least the season character of it. Still, that system held strong for over 20 years (and still manages pretty well with modifications), a feat that shames the older ones, which will be explored below.

Oddities and special numbers

Seasons six through nine of The Simpsons had a number of numbering quirks with hidden logic. It may be especially helpful to refer to air order to see how these episodes fit in.

• Clip shows (specifically, the 2nd through 4th of a total of 5), although considered real episodes, tend to have higher episode numbers. 2F33 and 3F31 leave sequence gaps and aired near the beginning of their production seasons (2F33 in particular may have been produced on extremely short notice, with episode numbers 31 and 32 already in use, see below, yet was also the first 2F episode to air), but share producers with the normal 2F and 3F episodes. 5F24, described in a later note, has some resemblance to this pattern. (9F17 and DABF12, the first and last clip shows, have nothing special about their numbering, air order, etc.)
• Several other episodes use high numbers to set themselves apart. In production season 6, which was executive produced by David Mirkin (2F01-22, 33), 2F31 (the crossover episode with Al and Mike's The Critic) and 2F32 were co-executive produced by former showrunners Al Jean and Mike Reiss (with Mirkin), and they aired in the middle of the season.
• Special episodes produced alongside season 7 (3F01-24, 31) did not get extra high numbers, but just a whole separate code prefix: 3G01-04. While the 3Fs were executive produced by Bill Oakley and Josh Weinstein, these were done by Jean and Reiss instead. These extra episodes ran during air seasons 8 and 9, beginning just after the 3Fs had finished. Why they weren't 3F25-28, or 3F32-25, I could not say. In some sense, the "G" marks them as almost a separate show, but perhaps this only matters to accountants. (The Simpsons Archive's Brian Petersen notes that codes would be assigned when the contracts were made, and possibly these four were intended for a special use, like home video or a summer season neither 7 nor 8; eventually they did become regular episodes in the regular schedule, even if 3G03 did have a special Friday premiere, but the codes wouldn't change.)
• Most of season 9 (5F01-22) was executive produced by Mike Scully, but 5F23 and 5F24 (clip show #4) were done by David Mirkin instead. They also aired near the beginning of the season, further cementing their role as "outside" episodes, even though the numbering was finally contiguous. It's possible that numbers like 5F31 and 5F32 were proposed but rejected. Anyhow, because of both producer and air order, it seems reasonable to consider 5F22 the main end of production season 9, as well as the 2-character prefix era (though see 9ABF notes below), meaning that distinction need not be granted to "a cheesy clip show!"

The two music videos from season 2 have codes 7F75 ("Do the Bartman") and 7F76 ("Deep, Deep Trouble"), although these do not appear onscreen even in the end credits. These are official (seen on slates provided to broadcasters but not meant to be broadcast); the 7F corresponds to season 2, and the choice of number seems to be, essentially, high enough to indicate them as special non-episode productions. More arbitrarily high numbers will be seen in other 20thCFT productions in this document.

Morgan Spurlock's documentary special, not considered an episode, gets a Simpsons-associated production code, too, the credits reading "THE SIMPSONS 20TH ANNIVERSARY SPECIAL IN 3-D! ON ICE!" (minus the colon usually seen after "special"), then "EPISODE LABF21" (no "#"). This aired a few weeks after the 20th anniversary of the series, following episode LABF20 (the maximum code in a short production season). It's a little odd to have the number contiguous, but that's what it says. Note it is twice the length of one episode.

The original Simpsons shorts from The Tracey Ullman Show are listed, for example here, with codes MG01-48 (MG=Matt Groening), though they do not appear onscreen. They're not 20thCFT codes, of course. However, I suspect these are official, in part because they do not match air order or production order of the Ullman episodes they were included in (see 4W/5W codes and dates in that list), perhaps a numbering system done locally at Klasky-Csupo to keep the shorts straight just as one would need to keep full episodes straight during production.

According to Brian Petersen and his sources, production season 9 used 5F and 9ABF in different places; "9ABFxx numbers began appearing on various internal documents right away, such as music cue sheets." 5F codes appear in the credits and seem most official; Brian speculates that it's "maybe because when all their scripts were originally written and printed, the 5F## numbers still hadn't yet been 'recalled' by 20thCFT yet" and notes that the first episode pinned with the alternate designation was 5F05 (9ABF05). Various shows during that 97-98 season did begin adopting the new system in onscreen codes at different points, as seen below.

Recent episodes in syndication, etc. (season 34 up?), have added a separate episode code to the non-English dub credits that have been inserted in those copies since about season 19. These include, for example, the Spanish title of the episode, as well as the standard production code, then the new alternative code, e.g., "E0732" for UABF21, apparently indicating a cumulative air order sequence. But that is episode 731 to air (counting WABF04/WABF05 as two), so why is it off by one? This highlights the problem with a system like this: it depends on too many factors, does not agree with the general consensus, doesn't appear on original broadcasts... it's nice, including allowing room for over a thousand episodes, but doesn't help outside a small range of use.

Most of the notes above benefit from the perspective of history, but shifting code systems did cause confusion at the time. Many old episode capsules on this site refer to strange entities such as [8[FG]01], reflecting the strange progression from 7G to 7F to 8F with no clear pattern. There may have been anticipation that a renumbering would occur, making the 8Fs into 8Gs or something. The notation is used for the 7Gs and 7Fs too, which is actually more confusing because a single reference could mean either of two episodes. The internal brackets, around "FG", may be an application of regular expressions. (The outer brackets are not really part of the codes but some people seemed to like them to set codes apart; they are seen often in documents here, newsgroup posts, etc., but have dwindled in usage.)
Because all but 17 episodes through the FABF series used nothing but digits and letters A to F, especially once the new ABF codes came about, they bore a superficial resemblance to hexadecimal notation (base-16 as used in computing), but of course that is just a coincidence, with the series letter being early in the alphabet just as the AB_ portion of the sequence is.

Production code references in the show

Even before the writers of The Simpsons knew how rabid fans would make use of the cryptic production codes, those codes began flavoring the show. Some notable examples (other good ones I've missed are welcome):

• Sector 7G at the Springfield Nuclear Power Plant owes its name to the randomly assigned code prefix for season 1. (Claims that it's the other way around require ignoring the way codes were assigned, or at least the very early cajoling of 20thCFT by a knowledgeable producer: "Hey, I know we're going to get a number-letter code, and the boys really like 7G for Homer's workspace in episode 10. Is that available?")
• Episode codes are often used within their own episodes when a similar string of letters and numbers is needed; a famous early example is the prisoner number of the character who'd come to be known as Snake, first introduced in 7F20 with that code on his uniform, and persisting through many appearances. Some one-off examples are in the Meta References page.
• In 4F12, in a scene poking fun at obsessive nerds, a flaw is indicated in Itchy & Scratchy episode "2F09". Note that Simpsons episode 2F09 actually has no I&S cartoon. The code "4F12" is also seen on an animation cel for Poochie's final episode, another example of the point above.
• During a Xena: Warrior Princess panel in BABF01, Frink pesters Lucy Lawless about continuity errors in her show, referring to made-up episode codes "BF12" and "AG4". Though these do not follow any code style, it's worth noting the similarity to the BABF codes this episode ushered in.
• In DABF15, Lisa's professor introduces Itchy & Scratchy episode "DABF06" (pausing oddly before the F) in a scholarly context; Simpsons DABF06 earlier in the season does have an I&S installment, though not the same one.
• In OABF06, Ned tells Marge that he was once Bart's teacher, seeming to cite an episode code before elaborating and keeping it a plausible non-self-aware statement: "You can look it up: CADF12. Those were his grades and the days he was absent. CADF12." This is extremely close to a modern Simpsons code, except for the D; B is still a grade, but perhaps makes too high an average for Bart, and anyway, keeping it fictional avoids needing to find a real episode that supports the claim. The enunciation is pretty good, though the second time it's full of little pauses.

General history and the phases of 20thCFT production codes

This is a general history of 20th Century Fox Television production codes, showing a gradual evolution through over 65 years and counting. For almost six decades, nearly all of these shows have put their production codes in the credits, allowing for direct examination without reliance on external sources. It's useful to see how Simpsons codes fit in (a show airing for over half of the period of onscreen codes!), or those of your favorite shows, but fascinating all on its own.

These are shows for which 20th is the production company, and that is not equivalent to airing on the Fox network. The company name has changed over the years, along with the official name on copyrights, end logos, etc., particularly after the Disney buyout, resulting in "20th Television" branding around 2020. Since this history is almost exclusively pre-Disney, the old name makes the most sense, along with abbreviations like "20thCFT" or just "20th". (Other names seen in credits and logos include Twentieth Century–Fox Film Corporation [alternatively with a hyphen or just a space between Century and Fox], 20th Television Animation, etc.) Onscreen codes are sometimes found elsewhere in the television landscape; notably, most Fox-related companies include them, and some are discussed later.

Sources, formatting, etc.

Brian Petersen of The Simpsons Archive is responsible for several dozen shows' worth of code information that seeded this project, along with other useful information and pointers. Episode lists at sites such as epguides.com, tv.com, and defunct feeder sites (as seen via Wayback Machine), plus Wikipedia, were good resources. Direct confirmation of many entries is due to some diligent TV viewing and the wide availability of home video releases, and unofficial Youtube archives of nearly forgotten shows. Special thanks to obsessive uploaders of split-screen and text credits meant to archive network/news promos! (One source I do not have is anything official at 20thCFT, though getting some historical inside information from production archives, studio memos, etc. would be great.)

In most of the grids and lists below, codes I have personally witnessed in a real broadcast, archive, or home video release are in bold (with hyphenation style to match); those I have seen the absence of are in italics. Some of these are full season confirmations, others a handful of episodes. Codes not in bold are unconfirmed (series not available to view, in most older cases, or not a priority) and may only be known from scripts and the like (particularly LOC records such as those Brian examined). It is possible that some shows' credits and code styles were modified between broadcast and home video release, though most display the odd mixture one would expect to be the very target of such revisions.

Years are frequently listed as 2-digit abbreviations, e.g., 96 for 1996; stylistically they should have an apostrophe ('96 or really ’96) but there are so many it would get messy. There should be no confusion over what century is meant, with dates ranging only from 1956 to the 2020s.

Since nearly all shows listed used the last two characters to represent an in-season episode number, I omit these and compare only the prefixes, apart from pilots and other singletons. Seasons are organized by traditional fall-to-spring calendar years, with midseason series and other oddities fit in as best possible. Holdover episodes (those not aired until the next broadcast season) are generally irrelevant here. Most wording and punctuation choices are generalized, too, with some series simply including codes, some using "#" or "No.", along with "Production" and so on. Combined multi-part episodes, which usually have two or more separate production codes (pilots being the main exception), tend to chain the codes together in full or without repetition of the prefix, joined by a slash, ampersand, the word "and"...; some notable examples are provided.

Tables are listed in premiere order. Footnotes under tables list out minor details and exceptions, even though half this document's content is essentially a footnote.

A note on pilots and TV movies

A pilot is a demonstration of what a TV series would be like, often in the style of a full or even double-length episode. It is used to sell the series and gauge interest with executives, focus groups, or the public to determine what series to pick up. Not all series have pilots (e.g., those whose appeal or style is already evident), and some are never broadcast; some may be short demo reels, some may have been retooled or recast enough that they don't match the final series. Other series run their pilots as their first episodes, possibly with some small changes, new credit sequences, etc., or do use them later in the season after some episodes that may hook audiences more quickly. In other cases, footage from an otherwise unusable pilot may be salvaged and integrated into a new episode (Star Trek's "The Menagerie" is a famous example). Production codes for pilots often have a special number or pattern, and those will be discussed in each era.

The pilot is not equivalent to or a synonym for the first episode of a series, although when the pilot or a mildly changed version is broadcast, it frequently is titled "Pilot" or the name of the series, so you're probably safe then. Animated shows seem more likely to have short presentation reels, about the length of one act, because of the expense of animation; for The Simpsons the Ullman shorts likely served this purpose, and calling any season 1 episode a pilot would be wrong. (Futurama's "Space Pilot 3000" and "Episode Two: The Series Has Landed" seem to be a joke about the usual live-action practice, not a real example of it.)

Unsuccessful pilots may be broadcast before or after the decision not to pick up their series. Some are aired to gauge viewer interest and may be branded as specials or (for suitably long double episodes) TV movies; if they already failed to get picked up, they may also run as TV movies to not be a total loss. This blurs the line between failed pilots and productions truly designed as TV movies (with no intent to start a series). In the grids and lists below, I've tried to figure out which is which, but I may call a failed pilot a TVM or special, or vice versa. The "season" such a production belongs to can be fuzzy too.

Unsuccessful and unaired pilots and demos of all types are often released as bonus features on DVD, etc., for example, with their successful series, or with theatrical movies they were meant to spin off from or old series they were attempting to reboot.

The 60s: 2-digit prefixes and the birth of onscreen codes

For the early days of 20thCFT, I can find only one set of reported production codes: the second season of Broken Arrow (56-58), 4-34 to 4-72, for episodes 34 to 72 of the series, apparently their 4th.

After that, we see four-digit episode numbers, with a two-digit prefix indicating the series/season (not able to be broken down further) and the usual in-season episode number after that. There are patterns here: for the most part, the second digit tended to remain the same for a series while the first was incremented by year, and even that first digit has a vague correlation to the calendar year. However, for most of the decade, these production codes were not shown onscreen.

Suddenly, across the board, in November 1966 codes began to appear in the end credits, typically stuck in near the bottom of the copyright page. Someone at the studio must have declared a new policy, for at least ten series rolled them out in the span of a month and I've found no holdouts. Some episodes with lower production codes yet to air remained code-free, some put the codes in, each series varying in its treatment, presumably based on the degree of production completion and ability to get it done. In this half season, it also took a few episodes for many series to integrate the codes into their usual credits style, with many early ones missing drop shadows, experimenting with layout and size, even making alignment and font/style errors. (In the grid below, bold prefixes for this season carry an implication of a partial season of unseen codes.)

In this period, codes were usually unadorned: mystery numbers hanging around at the bottom of the screen, maybe with a "#" in front as the decade went on. Multi-part episodes (each part aired on a different night) usually listed one numeric code shared between parts with a part-number suffix, skipping an adjacent number entirely, but there was no common system for this, and examples are listed below. This practice seems confined to the 60s.

Separately-numbered pilots were drawn from a special sequence. Besides the reported 3303 for Five Fingers in 1959, a sequence beginning with 60, then 62 (maybe 63), supplied pilot codes; this helped avoid wasting a prefix for a series that never got picked up, and once it did, if the pilot aired, the "01" episode number was skipped (see "01+", "02+" notes, etc.). At least two series list two pilot codes in their aired single-length premieres, suggesting a few attempts to shape them or perhaps a merging of two concepts. Some series, especially before onscreen codes, may have had separate pilot numbers not found in the grid.

Additional code numbers and oddities

• Special effects 2nd unit footage for the last three (color) seasons of Voyage to the Bottom of the Sea is included as a DVD extra, and its slates show the codes 8297, 9297, and 1394. This very nicely confirms the 82 prefix but also gives another good example of arbitrarily high non-episode production codes.
• Voyage to the Bottom of the Sea also provides one of the strangest code placements I've ever seen on DVD packaging. Official Fox DVDs of the first three seasons through 2007, on double-sided discs with only a thin circular strip of text as a label, indicated episode ranges per side, in cumulative order, ending in episode 84. The 2009 DVDs of season 4, volume 1 used the production codes! For example, "episodes 1301,1306". These also included "6008" for what is called the re-cut unaired pilot (in color), and apart from that one side the hubs' use of numerical order conflicts with air order, so the codes are slightly wrong in addition to being, I'm sure, utterly befuddling to most of the DVD owners. The printed box art/inserts include many episode details, but not these codes. And the final volume, in 2010, goes a third way, listing episodes 14-26 (of season 4). Little wonder. I've seen 2-digit episode codes on geek-friendly Star Trek menus alongside titles; I've seen codes in production order on Rhino's old MST3K DVD boxes; are Voyage fans nerdy enough to appreciate this? (By the way, its first episode is variously reported as 6008 and 7001; could it be that 6008 is the color pilot, and then the B&W first episode got a new code, possibly 7001 or even a misread 7201?)
• Batman onscreen codes are already odd (literally), as noted below, with a variety of multi-part numbering systems, but after the half season of inclusion in the credits, they are completely absent for season 3! Why? Apart from Journey to the Unknown, which was only distributed by 20th, all other series of the time seemed to include codes. (See also 80s!)
• Peyton Place goes its own way after playing along with the onscreen code style for a while; see footnote below.
• Several series are missing episode codes, suggesting they were abandoned during production, possibly with new codes at the end of the sequence added in. These early examples include (or don't include) Five Fingers 3715, Adventures in Paradise 3505, and Voyage... 8208. Skipped codes become less frequent as the decades go on; my hunch is that later episodes in a production run are moved down to fill a gap.

	59 -60	60 -61	61 -62	62 -63	63 -64	64 -65	65 -66	66 -67	67 -68	68 -69	69 -70	Notes
The Many Loves of Dobie Gillis (Dobie Gillis)	34	44	54	64								01+; see also 5T79
Five Fingers	3303 37											02+
Adventures in Paradise	35	45	55									01+
Hong Kong		41										01+
Bus Stop			53
Margie			57
Voyage to the Bottom of the Sea						6008 72	82	92	13			02+; pilot also listed as 7001
Peyton Place						??	??	90 91	22 ###*	###*		### = episode # (397-514)*
Valentine's Day						6010 75
12 O'Clock High						6011 73	83	93				02+?; 2-parter 7329 on both?
Daniel Boone						6013 74*	84*	94*	14	30	50	02+; 2-parters vary*
Lost in Space							85	95	15			01+
The Long, Hot Summer							20
The Loner							21					01+; 2122-A/B
Batman							6028 87	97	17		03+; S1/2 odd #s; "-I"/II+"-PT. 1"/2/3*
Blue Light							6026 88					02+
The Monroes								6031 81				02+
The Tammy Grimes Show								11
The Green Hornet								98				01+; "-PT. 1"/2*
The Time Tunnel								6034 96				02+
The Felony Squad								89	19	29		2-parters vary*
Custer									6045- 6050 25			"#6045-6050" dual pilot #; 02+
Judd for the Defense									6044& 6012 18	28		"6044 & 6012" dual pilot #; may use -1/2
Julia										6203 38	48	02+; "part i"/ii E-3 (see below)*
The Ghost & Mrs. Muir										6205 32	52	02+
Land of the Giants										24	47	01+
Lancer										6208 31	51	02+; older pilot blurry (6006?)
Journey to the Unknown										39		01+; 20th distr.
Room 222											6215 49	02+; 4 more (see below)
Bracken's World											6318 58	Or 6216?*; 02+?; E-2 (see below)
Nanny and the Professor											6221 59	02+; E-4, F-4 (see below)

Table 1: All-numeric codes (up to 69-70).
*Peyton Place was a prime-time soap opera, airing 2 or sometimes 3 times a week (just weekly in the final few months) and never taking a break, with 514 episodes over nearly 5 years! Like every other show I've found, it began displaying 4-digit codes in the credits in late 1966, but because it didn't have typical production seasons, and did often have over 100 episodes per year, the numbering systems didn't quite fit it. I have no idea whether earlier episodes had official 20thCFT numbers or what they'd be (maybe a 7_01-99 and 8_00-99); perhaps a memo went out that all shows needed codes onscreen and these numbers began getting assigned right here (though in that case I'd expect an 01 or 22ish). Anyhow, episode 289 (11/23/66) was 9089, 9099 gave way to 9100, and as September 1967 and the start of a new broadcast season rolled around, 9167 led to 2268 (episode 368, 9/7/67). These three prefixes all fit with other shows'. Yet I guess someone at PP wasn't terribly happy with this system, perhaps not looking forward to getting a prefix to follow 22; before the digits could roll over, 2296 led to simply the sequential episode number (397, 12/25/67), which remained in that spot through the finale (514) in June 1969.
*Daniel Boone's season 1 two-part episode has 7426 listed for both parts, and one in season 2 gets separate codes of 8429 and 8430, but none of these are onscreen. In season 3, a two-parter is "9416-PT1" and "9417-PT2", having both separate numbers and part designations.
*Batman is wild. Seasons 1 and 2 aired twice weekly with 2- and sometimes 3-parters, and that's probably why only odd numbers are used, with part numbers. Season 3 was weekly but had several multi-part episodes, using the same idea (and even numbers, though multi-part episodes are still odds!). It all balanced in the end, with extra parts causing some sequence gaps rather than lower maxima. When codes started appearing onscreen, they were "-I" and "-II" for three pairs (9725, 9727, 9729) and then "-PT. 1" and "-PT. 2" (and 3) thereafter (even on the late-airing 9715). Inexplicably, as noted above, season 3 seems to have dropped onscreen codes entirely!
*The Green Hornet has several two-parters, though one was before codes were shown, the others using "9818-PT. 1" and "2" (and 9825), skipping 9819 and 9826, like Batman. Some guides just list them as 9818/19/25/26.
*The Felony Squad I could only find a few episodes of, enough to spot one an "8921 PT 1" in season 1 and "1913" on its own for part of a two-parter in season 2, suggesting it may have stopped that notation. I can't confirm or deny a separate pilot code.
*Julia has one two-parter listed onscreen as "#4827 part i" and "ii" (lots of space after the episode number, lowercase like the rest of the credits) and no 4826, though some guides list them as 4826 and 4827.
*It's hard to make out the code on the Bracken's World pilot in the copies I've found, and I don't see it documented anywhere. Second digit might be 2, fourth might be 6, or I might be further off. Better info is welcome!

The 70s: random letters and numbers

The numbers were not going to hold out forever. By the end of the decade, over half of the available prefixes appeared. For the 70-71 season, existing and new shows alike would feature a prefix with a letter and one digit instead. This was orderly at first: that season's letter was E, perhaps to evoke the word "episode" (see notes on confusion below). Then F. G would usually follow, but a random letter order that I cannot explain took over. Most seasons did have one or two letters for full season prefixes, with numbers assigned haphazardly (renewed shows didn't retain a semi-consistent number); though there is some broad order as seen from a distance, rote memorization is all one can rely on for tracking a series across multiple seasons. If you thought 1F and 3F was hard, you don't want to try to remember M*A*S*H codes. Through the 90s, the main letters not seen in prefixes are I, O, and Q; U is consistently used, and other exceptions may just be undiscovered and not forbidden.

Pilot codes varied. One remnant of the 6x sequence is the failed pilot They Call It Murder (6701), which did not air until 71 but was produced in 69-70, perhaps while the the sequence was still moving along. But for the bulk of the decade, pilots, TVMs, and other presentations got one of two things: Z-#### (four digits with no apparent pattern) and a letter-number combination dedicated just for this purpose. Most but not all of the latter use the digit 9, and I assume there were dozens of pilots that never made it but drew from these sequences. Most of the "episode" numbers are low, but examples go as high as 10, and the two failed pilots from 76 show the prefixes did get repeated. Only a few of those codes don't use 9, and 9 is rarely (if ever!) used in regular prefixes. (Hagen is the main exception here and I've yet to confirm its partially reported codes!) By the middle of the decade, skipping the "01" episode no longer occurred, whether there was a separate pilot code or not.

For the 70s and early 80s, codes migrated a little higher on the screen but still generally occupied a space of their own, not explaining their role. With rare exceptions, these new codes contained a hyphen (or dash, if you like) between the letter and the digit of the prefix, probably to set apart the character sets, yet resulting in an apparent but meaningless three-digit number (better than an apparent but meaningless four-digit number?). As with every single other evolution of code styles, it caused some confusion for both producers and viewers. The first episode of Room 222's season 2, though not the first to air, was listed as #E501 (the only "#" in 5 seasons); similarly Bracken's World had what looks like "E#201" before finding the hyphenated style. Whether "E" came from "episode" or not, it surely could be taken that way (at least for Bracken it did work as "episode 201"!), and between the inaugural "E" season and the separating hyphen, it paved the way for fan guides to omit the letter entirely (even in 2009 I had only the numbers for Room 222). Occasional shows dropped the hyphen or replaced it with a space throughout the decade, sometimes just for an episode or two! (Confusion between "0" and "O" also reared its head sometimes, as in The Paper Chase's pilot that appears to say "X-91O", but maybe it's an aesthetic choice. Yet more than once, into the 90s, I've seen O1 to O9, then 10, 20, etc. and 01-09 on subsequent seasons. I am not reporting these as a general rule.)

Oddities

• M*A*S*H offers a variety of double-length two-part episode code styles, though mostly they are variations in punctuation: U-801 — U-802, Y-101 Y-102, Z-419-Z-420.
  On DVD at least, one is shown just as G-504 (without mentioning its second half, G-506); T-408 and T-409 survive only as divided syndication edits and list just one code on DVD no matter which viewing option is selected (and it appears to always be 08 but it's too blurry to tell)!
  Curiously, the massive grand finale, 9-B04 (a preview of 80s style for you), is about five times the length of a single episode, with an episode number from the middle of the sequence, yet just has that single code.

68 -70

70 -71

71 -72

72 -73

73 -74

74 -75

75 -76

76 -77

77 -78

78 -79

79 -80

80 -81

Notes

Julia

6203 38 48

E-3

Room 222

6215 49

E-5

F-2

J-1

K-3

"#E501", "E-502"+

Bracken's World

6318 58

E-2

"E#201", "E-202"+

Nanny/the Professor

6221 59

E-4

F-4

Arnie

E-1

F-3

01+?

Cade's County

F-1

01+; "F124"*

Mr and Mrs Bo Jo Jones

F801

TVM Nov. 71

They Call It Murder

6701

Pilot prod. 69-70, aired Dec. 71

Anna and the King

H-901 J-2

02+

M*A*S*H

Z-9522 J-3*

K-4

B-3

G-5

U-8

Y-1

T-4

S-6

Z-4

02+?; 1-G, 9-B (see below)

The New Perry Mason

K-1

01+

Roll Out!

K-7

Pilot no code?

Planet of the Apes

B-5

01+

The Mark of Zorro

C-901

TVM Oct. 74

Karen

D-9

01?

Swiss Family Robinson

G-201 M7

01+; closer to "M 7"

Time Travelers

R-903

Pilot Mar. 76

State Fair

R-904

Pilot May 76

That's Hollywood

U-3

T-1*

1K (see below)

James at 15 (James at 16*)

Z-2978 Y-4

01+; "Y 408", "Y 402" +?

The Paper Chase

X-910 T-7

01+; cont. 80s (see below)

Trapper John, M.D.

A-910 V-4

Z-5

01+; 5 more (see below)

Swan Song

S-901

TVM Feb. 80?

Hagen

S-401 ?-9*

01+

Breaking Away

Z-902 Z-6

01+

Table 2: Letter-number codes (70-81) and overlaps in both directions for convenience.
*Cade's County has at least one code presented with no hyphen, and may have some with a space. It also has at least one two-parter compilation, whose parts I suspect but cannot yet confirm had regular F-1 codes, aired as a TVM: "Slay Ride" (Z-9523?), with others seeming to have no onscreen codes at all. The long Z code fits with other special presentations, but I'd love to get more info on all of this.
*The first episode of M*A*S*H has this Z pilot code on DVD, though some guides list it as J-301. I'm going by the only screen evidence I have.
*That's Hollywood has been hard to find much information about at all, such as episode list or airdates, let alone codes. There seem to be just three production seasons, though. The few early episodes I've been able to find do not seem to have onscreen codes, but I'm not sure whether they're U-3 or T-1 (both, I think). I have seen some onscreen 1Ks.
*James at 15 became James at 16 halfway through the season, crossing out the old age in the title sequence, and this change goes with air order, not production order. By the way, a previously-reported "905" pilot code I saw in a guide seems to be based only on its airdate!
*Hagen guides list the pilot as S-401 and the rest as 9__ (including a 901). I assume the letter was ignored there, as it was in guides for many shows around this time.

The 80s: random numbers and letters

Starting in 81-82, there was another change: the prefix became digit-letter, not letter-digit. This, in some form, has been the basis for all main sequence codes since. The randomness continues, with a vague association of a digit to a season, but even looser than the letter-season combinations of the 70s. After starting off nicely with 1, it seems to go backwards for a season, dabbling in 9, 8, and even 7, then proceeding loosely through 2-7. Letters are utterly inconsistent, even more random than the digits of the 70s, and it was the rare show indeed that kept the same letter through even two seasons (The Tracey Ullman Show may be the only no-change series, though Anything but Love's letter was consistent through this period). Of course, it is at the end of this period that The Simpsons got its 7G.

However, for some reason, several shows did not include production codes in their credits (through the early 90s). These are all 20thCFT shows, as far as I can tell, and although some exceptions to the code patterns described have existed, shows with regular codes generally did display them. If there is a common trait, I am not sure of it, although it seems most or all of the shows in question were taped and not filmed, so perhaps a different postproduction unit was in charge. I'd love to figure this out.

Pilots changed several times, too. I see three last examples of entirely separate pilot codes for 83-84, two of them with a 9C prefix (compare the use of 9 in 70s pilot codes). In mid-84, there is a TVM, Love Thy Neighbor, with code 3K99, and a failed pilot for yet another M*A*S*H spinoff, W*A*L*T*E*R, whose code is hard to read (and in parentheses!) but might be 3A99, or 2A99, or another high episode number. This is likely a move toward the long-lived practice of devoting a whole prefix to a series right away with a certain special pilot episode number.

As early as 85-86, or 86-87 with better "really a pilot" evidence, TVMs and pilots began getting their own prefixes and using episode number 79. This special number stayed in use for nearly 30 years (or maybe longer)! It also found its way into other Fox-related systems. Why 79? Apparently 99 was no good, and this was just right: high enough to be out of the way, low enough to leave some very high numbers reserved (perhaps for more internal stuff like Voyage to the Bottom of the Sea 2nd unit). Maybe it was a misread 99 and it stuck. It seems unlikely to be a reference to the year, or an homage to the number of original Star Trek episodes or anything. Many 79s were aired as episodes, and at least a few became reworked into 01s (see Dollhouse for example), but the general rule from this point on is that new episodes start from 01, so a typical 22-episode season might be 79 and 01-21. As usual, some series just began with 01, including some that called the 01 (or 01 and 02) the pilot.

Later in the decade, the codes began migrating into blurbs of legalese as little afterthoughts, hanging out next to an "all rights reserved" or "Twentieth Century Fox Film Corporation"; some stayed in their own space but added "Prod." or something similar.

Under this system, the hyphenation began to drop out. It's not a surprise; 1-E01 means just as much as E-301 (which is not the three hundred first of anything or third of something/first of something else), but why mix letters and numbers on one side while separating them on the other? There's no pattern to this, but just as many little exceptions. Partway through its first number-letter season, M*A*S*H switched to the more logically separated "1G-11" through "1G-24", but then back to "9-B" the next year, mixed with "1G-" holdovers! The last hyphenated codes I've seen are on Heart of the City (86-87), and yet the practice remained in the industry for years after that: I have seen a 1997 syndication schedule for The Simpsons meant for TV stations that lists episodes as old as "7-G12" and as new as "3-F16", despite the total lack of hyphens in this show's codes. Brian's feeling is that either hyphens persisted officially through the 90s but gradually got dropped by producers, or they were dropped at the start of the 80s but well-meaning producers, schedulers, etc. kept reinserting them, assuming their omission was a mistake. In some places, old habits die hard.

Additional code numbers and oddities

• The Fall Guy uses only odd episode numbers for its first two seasons; its double-length premiere is just 1-E01, and then the rest are 1-E03, 05, etc. Some pilots/premieres of that length take up an 01 and 02 (listed or not), which would explain starting from 03, but this is puzzling.
• At least one Tracey Ullman Show special has an arbitrarily high episode code, which I think is 5W75 (it's hard to make out).
• Several 80s episodes of The Paper Chase seem to be confused about their codes, at least on DVD (noted for relying at times on secondary/syndication sources), some swapped or doubled up, 4M01 missing a code entirely, but it's possible they were originally broadcast correctly. The double-length grand finale uses the most compact designation "4M05/6".
• In the whole decade, the only skipped episode code I've spotted is 9 to 5's 2C08; that series also combines its last two seasons' codes as 4V01-26 and 4X27-52.
• The pilot for The Highwayman has 20thCFT code 5L79, but the rest of the series uses a different code system because it was picked up as a series by a different company.

	70s	81 -82	82 -83	83 -84	84 -85	85 -86	86 -87	87 -88	88 -89	89 -90	Notes
M*A*S*H	^	1-G	9-B								"1G-11" to "1G-24"
That's Hollywood	^	1K
The Paper Chase	^		8-C*	2V*	3M*	4M*
Trapper John, M.D.	^	1-M	8-B	2-F	3-L	4-J
The Fall Guy		1-E	7-B	2-G	2-Z	4-E					01+; S1/2 odd #s only
9 to 5		1U	2C	1S			4V	4X			01+; 4V01-26, 4X27-52
Trauma Center				?? 2-H							Pilot code unknown; 01+; "2H07"
AfterMASH				2-E	2-W						01+
Emerald Point N.A.S.				2-K							"2-K01/02" on pilot
Manimal				3-D01 2-L*							01+
Automan				9-C09 2-M*							01+
Masquerade				9C-03 2-J							01+; "2J03" on first aired of 2Js
Love Thy Neighbor					3K99						TVM 5/23/84
W*A*L*T*E*R					3A99?						"(3A99)"/2A? 7/17/84*
Cover Up					3-J					"3J01/2" pilot, "3J13"
Mr. Belvedere					3T	4G	5A	5M	5V	6V	01+
Half Nelson					3U						01+
Charlie & Co.						6S					79/01+
A Letter to Three Wives						3-N79					TVM 12/16/85
Fathers and Sons						6U
The Wizard							4P				79/01+
L.A. Law							4L*	5K	7A	7D	01+*; #L (see below)
Heart of the City							4-S				79/01+
The Tracey Ullman Show							4W* / 5W*			7W	01+
The Highwayman								5L79			8801+ non-20th series
Hooperman								5J	6X		01+
Second Chance/Boys Will Be Boys								??*
Leg Work								5G			79/01+
Bring Me the Head of Dobie Gillis								5T79			TVM Feb. 88*
Anything but Love									5Y	6Y	01+; #X (see below)
Have Faith									5R		79/01+
Sister Kate										5Z	01+
Alien Nation										6W	79/01+; see also 1N79
The Simpsons										7G	01+; #F+ (see below)
In Living Color										7H	01+; #U (see below)

Table 3: Random number-letter codes (81-90), no overlaps. (^=see 70s.)
*The last four seasons of The Paper Chase aired mostly in spring-summer runs from 83 to 86; I filed them this way. Note also that guides and DVDs call both 8-C and 2V season 2 and title cards say "the second year", but looking at airdates and production codes I say they're separate.
*Manimal and Automan are hourlong shows with 90-minute pilots. I'm not listing every extra-length pilot but clarifying an earlier version of this list noting my confusion since I wasn't sure whether I was looking at pilot/series or TVM/spinoff.
*W*A*L*T*E*R (pilot): see description above.
*L.A. Law uses 4L01 for its double-length pilot and 4L03+ for the rest of season 1, suggesting the pilot's second half may be counted as 4L02.
*The Tracey Ullman Show is kind of odd; the 4W and 5W seasons, as marked, correspond to the calendar seasons they began, but two production seasons were stretched into three air seasons, and 7W is the third production season and 4th year/air season. The numbering might reflect an attempt to keep order by skipping an unproduced 6W season, or maybe Alien Nation had already scooped up that code.
*Second Chance and Boys Will Be Boys, two shows resulting from severe retooling midseason to cancel one but retain star Matthew Perry, make up a single broadcast season with seamless coding, but no onscreen codes and no help from the net leave me stumped. Maybe they had 5_ or 4_ codes, maybe nothing of the kind, but I'd still like to list it.
*Bring Me the Head of Dobie Gillis is the second followup to the series, and may have been meant as a TVM or pilot for a reboot, airing in February 88. The first followup, Whatever Happened to Dobie Gillis?, was a failed pilot for a reboot, airing in May 77, and not only can I not find a code for it, it may be lost.

The 90s: meaningful numbers and letters

Finally, by the 90-91 season, there was an across-the-board attempt to standardize codes. The digit-letter prefix was still used, but now each digit represented a split calendar year for the broadcast season, and each letter represented one series consistently. It seems possible, based on proliferation of examples, that some letters were chosen or requested purposefully for this system. (After 7-9, digits wrapped around to 1-5; 0 was skipped, and 6 never had a chance to be part of this system.) Pilots almost entirely use the 79 episode numbers (when applicable).

Shows carried over from the 80s, at least those I know of, were assigned new letters, mostly because the bulk of them had 7_ codes in 89-90 and 7 was the digit for 90-91! I suspect that, with the risk of overlapping codes between the 80s and 90s versions (hyphens or not), 7 was chosen to maximize the amount of available ones for the longest time (it had just been in use but not for many shows, and 8 and 9 were barely used). The first overlaps I see are between 93-94 and early 80s codes; most pertinent to this site are Simpsons 2F and Trapper John 2-F. Any overlaps at all are not ideal, and prevent a 20thCFT-wide claim to uniqueness, but it still worked pretty well.

As was discussed above, The Simpsons got letter F (with a dash of G), moving into its second 20thCFT code system, and nearly breaking it by season 9!

Around this time, more series began to label the codes as "Production (#)" or even "[series name] episode #", but plenty left them in the middle of the screen, perhaps with just a "#".

The only point of confusion seems to be the Simpsons-specific "[FG]" stuff discussed above, and a bit of letter-number misreading. There was a lot of consistency: except for seasons from the 80s, the codes are easy to learn, keep straight, and anticipate. The first digit only identifies the year, not a show's own season, but knowledge of the show's premiere date helps. (Shows begun in 93-94, like The X-Files, do also happen to match season number to that digit.)

Additional code numbers and oddities (see also Simpsons section above)

• Early season DVDs of King of the Hill make extensive use of production codes to refer to episodes, not in the packaging, but in the menus, where episode titles and airdates are accompanied by codes, a list of music selections is indexed by code (and for nerd overload also includes music cue numbers like 2M2 and 3M7), etc. Curiously, the season 3 menus for season 2 holdovers list them as 2ABE even though the in-episode codes are still 5E; see transition notes in the next section and backnumbering under Fox in Flight.
• It took just over two seasons for In Living Color to include codes onscreen, with a little 1/I confusion (see footnote). Also, episode 8U14 seems to be skipped (dropped for a Michael Jackson special, 8U27, and never produced?), and season 3 included 8U27-30 as specials and clip shows mixed in with normal episodes (which went up to 8U26). In season 4, with a jump in sequence, 9U40-45 were best-of clip shows mixed in with normal episodes.
• Dharma & Greg begins its run with AE codes (see transitional hiccup in footnote), rather than 5_ codes. Could it be that the 5_ codes were exhausted during code assignment for this season, and an A_ sequence stopgap was instituted and maybe even the last straw before the new system (below) came about? If I could find AA-AD codes, maybe for failed pilots, that would help.
• The Pretender is another rare series in this period with a skipped episode number (see also NYPD Blue below): no 03105. See footnote for more on the strange code system; a non-20thCFT show at first, it was originally an MTM one, and MTM was no stranger to skipped episode numbers!

"21st Century Fox": three letters for a longer-term fix

By the end of the 90s, a problem arose. There would be a "6" year soon, and after that, another "7"? Letters can be changed, but only so many times. 5 may already have been exhausted. The next evolution was bipartite: the absolute year digit would change to a relative season number, and the single-letter series identifier would become a 3-letter one. Existing, continuing shows would have to make a change in production code style. Most shows got their current letter after "AB", so for The Simpsons, ABF. (Buffy the Vampire Slayer is a notable exception, see below.) New shows from then on would use a few remaining "AB_", "AC_", and so forth.

Brian's LOC research has shed some light on "AA_" codes, though it's unclear when these were assigned. They seem to apply to series with 3_ and 4_ prefixes, as if to reserve new three-letter codes in case of renewal. The examples: AAF = Fire Co. 132 (4B, set for 1AAF codes despite being a retooling of a series with 3B prefix), AAK = Picket Fences (ended with 3K), AAN = Relativity (4H). Only one of these letters matches; none of these new codes appear in aired episodes.

Even the 5_ and AB_ codes had some conflicts and oddities. Not equivalent are 5K (Nothing Sacred) and 1ABK (That's Life), whose aired episodes overlapped by about a week; neither are 5R (The Visitor) and 1ABR (Getting Personal), which had a few months between their air runs. In fact, according to Brian, The Visitor also has ABV codes; ABR seems unavailable, but by taking ABV it may have stopped Buffy from keeping the letter V!

Onscreen, this system was rolled out in the middle of the 97-98 (5) season, with some series changing code styles suddenly yet at different times in the spring, and others waiting until the new 98-99 production season (see footnotes under Table 4). Some fan guides (and even LOC, e.g., for Buffy) listed "6" codes but all onscreen evidence reflects the new system. Holdover episodes and those aired after episodes with the new codes generally did not get adjusted (e.g., Simpsons 5Fs in air season 10, including after AABFs had begun; ...Pizza Place 5Zs of lower numbers in with 1ABZs of higher numbers).

Just as The Simpsons nearly broke the previous system by running through most available digits, it started off the new one by immediately posing a problem: it was about to begin season 10, well-known as a non-single-digit number. The numeric sequence was extended to the alphabet: 10=A, 11=B, etc., making season 10 start with AABF01. Fans expecting a 6F01 or something similar had to make some sense of this, some interpreting it as AAB-F-01 rather than A-ABF-01; a change a season or two earlier, to an 8ABF or 9ABF, would have made it a little clearer. (See also the note about 9ABF05 and similar internal codes, which did not appear onscreen, above.) But whether the longevity of the series had little or much to do with the forward-thinking decision to switch systems, that switch happened without much time to spare!

It's worth noting that this system does trade one piece of encoded information for another: for the 90s system it was possible to determine broadcast season from a prefix, but not the season of a show (without additional knowledge); now it was the other way around. The new system is also more resilient in adding continuity to series with long hiatuses or revivals, simply picking up where they left off. Family Guy and Futurama survived cancellations without prefix gaps, along with Arrested Development and Last Man Standing. On the other hand, some series were revived without using their old three letters, and whether the system was misunderstood or the bureaucrats considered them separate series I can't say. The X-Files and Prison Break come to mind; 24 did a little of each approach (though its new letter trio really stood for basically a new series)!

Some confusion still existed, not just among viewers. It's mostly little things, like the brief omission of the "1" season digit in Dharma & Greg during the switch, or the reintroduction of the hyphen in Titus. And one production house seemed to resent the whole thing (see David E. Kelley section).

For both series codes and alphanumeric season numbers, however, a few letters were off-limits, or at least saved for marginal uses. (Of all the developments in this document, by the way, this was the first I got to observe in real time!) These are I, O, Q, and U, and they seem to be skipped primarily to avoid visual confusion at low resolution or with bad signals. I looks like 1 (and J), O like 0 (and Q=G/O, U=V?). U is a real surprise, especially since it appears in all three previous systems. Series codes only use these in retroactive coding or Kelley shows, as far as I can tell.

And the season numbers skip them, too, or did, until The Simpsons once again broke the system by lasting beyond a previously unthinkable 31 seasons! What comes after Z? QUO, of course (and then a resigned flip to 2-digit season numbers). They weren't so forbidden after all! See Simpsons history above for more details. Anyhow, that makes the Simpsons alphabet ABCDEFGHJKLMNPRSTVWXYZQUO (no I). Not the most intuitive, even compared to an abridged but orderly alphabet. It gets worse: for reasons beyond me, Family Guy (the second show to get this far) skipped G, while American Dad! (third) did not! One needs to know the specific show's code history to interpret a season letter now. See above for FG future code speculation.

While the main sequence of A__ codes rolled out like license plates, ticking over about one middle letter per year (a decent way to estimate a show's debut), other 20th-related codes were springing up with similar structure. I haven't explored these as much, but the main set I've found all come from offshoot Fox21: VA_, RAG (the only example of this first letter I've found), and WA_ (various years until corporate mergers around 2014). Meanwhile, Fox company recoding and internal coding (see Fox Television Studios and Fox in Flight below) used up a number of Y__, B__, C__, D__ codes, some with letters before numbers instead of between, or so it would seem.

What comes after AZ_? Not BA_, but LA_! This rollover occurred in 2017, and yet, after just a few years, there seems to be a move away from this sequence, or a splintering of sub-companies, perhaps coincidentally timed with the Disney buyout. There's a lot more to learn as this develops. Some codes are listed below.

One more major change and abandonment of longstanding tradition: pilots continued getting 79 episode codes during this three-letter system, even at other Fox studios. But the last main sequence one I've seen is for The Crazy Ones in 2013, as well as a few Fox21/FTS series in the next several years. Has 79 been 86ed?

Additional code numbers and oddities

• A special for Family Guy's "100th" episode, not counting as an episode itself and airing during the tail end of the 5ACX series, got the arbitrarily high episode number 6ACX45. Curiously, a similar "200th" episode special has no apparent code (such as AACX45) and may not have been produced by 20thCFT. A spinoff special, Seth and Alex's Almost Live Comedy Show, received the code 1ARX01, appropriate for its 2009 airing, and may have used that entire ARX identifier all for itself.
  Family Guy also has one of the highest contiguously-numbered production seasons, reaching 4ACX35 (vs. a typical contemporary maximum of about 22) for its triumphant 2005 return. (It's true that three of those 35 were originally released as a DVD movie, but they have all aired as single episodes too, and 32 is nothing to sneeze at either.)
  (Poking into skipped-number territory, 7ACX10, "Partial Terms of Endearment", has never aired in the US, though it got a swift DVD release, so it's hardly missing or un-accounted-for, yet looking at a list of airdates and codes one might be confused by its absence.)
• 24: Redemption, a special TVM before season 7 and after a gap year, has the code 7AFF50, though its extended version with more cinematic end credits lists no code at all! The later Live Another Day season after season 8 resumed coding with a 9AFF prefix; 24: Legacy with a new cast received the AZK identifier.
• Prison Break's grand finale was 4AKJ22, but a DVD-only double-length "Final Break" released around the same time got designated "4AKJ23 & 4AKJ24", with an unusually fancy "Et"-styled ampersand compared to the typical one seen in other double episodes. Its later Resurrection "event series" got a new identifier, AZM.
• American Dad! is worth singling out as a series that, like The Simpsons, enjoys using its own production codes as license plates, etc.
• Several season 2 episodes of ...Pizza Place list an (R) after their codes, at least on DVD. Could it stand for revised, repeat, ...?
• Season 1 of The Simple Life lists episode codes as "The Simple Life Episode 101", etc., in the full-screen DVD credits anyhow. Season 4, the only other one I have been able to sample, uses a more typical style, though typographically suspect, 3AHZ01 and up, leading me to wonder whether the first three air seasons are two production seasons, what 2 and 3 look like, whether 1 aired with AHZ codes, etc.
• Previous research for this document turned up AFE codes for The Bernie Mac Show (see Fox Television Studios), which would be right for the date, but it wasn't a 20thCFT series. Or was it going to be, and assigned a code? (Onscreen codes and episode guides all seem to use the FTS system.)
• Purely in the realm of the silly and unofficial, but enlightening: in my 2009 web search for codes, "1ACL01" turned up a fictional epguides.com-style episode guide for 11 seasons of an imaginary spinoff of The Simpsons, The Lovejoys. It was "set" for a 2015 premiere, but the author didn't seem to know that the ACL code indicates that the show'd been in development since 1998. Fortunately, the projected finale (BACL17/18) was dated 5/15/25, so as of my 2024 update, you still have time to catch it in the author's head! Other silly stuff like this is elsewhere on the web, with other imaginary series (such as now-lost ACP examples and most non-Simpsons) using a variety of code styles.

A list of code/series assignments follows Table 5. First, there's another transitional matter to discuss.

86 -89

89 -90

90 -91

91 -92

92 -93

93 -94

94 -95

95 -96

96 -97

97 -98

98 -99

99 -00

Notes

L.A. Law

4L 5K 7A

7D

7L

8L

9L

1L

Anything but Love

5Y

6Y

7X

8X

The Simpsons

7G

7F

8F

9F

1F

2F

3F 3G

4F

5F

AABF

BABF

In Living Color

7H

7U

8U*

9U

1U*

Poochinski

7P79

Pilot 7/9/90

Working It Out

7V

50?/01+*

True Colors

7T

8T

01+*

Babes

7E

79/01+*

Good Grief

7Y

01+

Drexell's Class

8G

01+

Picket Fences

9K

1K

2K

3K

79/01+

Rhythm & Blues

9R

79/01+

The X-Files

1X

2X

3X

4X

5X

6ABX

7ABX

79/01+

South Central

1S

79/01+

Wild Oats

2W

79/01+*

Chicago Hope

2M

3M

4M

5M* 4ABM

5ABM

6ABM

79/01+

The 5 Mrs. Buchanans

2B?*

79/?

Alien Nation: Dark Horizon

1N79*

The Crew

3W

79/01+

The Preston Episodes

3E

79/01+

Cleghorne!

3L

01+

Space: Above and Beyond

3S

79/01+

L.A. Firefighters (Fire Co. 132)

3B

4B*

99?/02+?

The Pretender

031*

032*

3ABP

4ABP

01+

Relativity

4H

79/01+

Millennium

4C

5C

3ABC

79/01+

King of the Hill

4E

5E

3ABE

4ABE

01+

Pauly

4P

01+?

Temporarily Yours

4T

01+

Buffy the Vampire Slayer

4V

5V

3ABB

4ABB

01+

Secret Service Guy*

4D

79/01+

413 Hope St.

5W

79/01+

Nothing Sacred

5K

79/01+

The Visitor

5R

79/01+

Dharma & Greg

AE* ABD 1ABD

2ABD

3ABD

79/01+

Two Guys, a Girl, and a Pizza Place (Two Guys and a Girl)

5Z* 1ABZ

2ABZ

3ABZ

79/01+

Table 4: Orderly number-letter codes (90-98) and three-letter codes (98+), with overlaps.
*In Living Color does not show any codes for 2 seasons (and 2 episodes of season 3); the first code seen is 8U03. For most of season 5 the code is typed as IU and I consider this a typographical mistake like 0/O, especially since it was corrected for 1U18 and up, and two earlier episodes (on DVD at least, not sure whether they aired this way, since the credits are in a different style) say "1U 05" and "1U 08".
*The pilot of Working It Out does not have the code onscreen either, and guides report it as an anomalous 7V50; I have not been able to find other episodes to check out.
*At least one episode of True Colors doesn't have the code onscreen, though most do; this one seems to be 7T15.
*The pilot of Babes does not have the code (7E79 according to guides) onscreen. Other episodes do.
*Alien Nation (6W, 89-90, see above) ran for just one season, then returned as 5 TV movies from 94 to 97. Only the first of these, Dark Horizon, shows a production code, suggesting to me that it was produced as another double-length pilot for a failed reboot (for 93-94), but spun into a series of TVMs, the rest not assigned codes since they were neither pilots nor episodes (and TVMs without codes by then?). 1N79 did not air until October 1994, though.
*An unaired 5th episode of Wild Oats seems to be missing the copyright page (and code) entirely.
*Chicago Hope switches format in the middle of season 4. Brian's notes suggest 5M14 to 4ABM15, but epguides.com has 5M15 to 4ABM16. I'd love confirmation, especially from original airings.
*Guides for The 5 Mrs. Buchanans list a 28 prefix, and I'll be darned, it's hard to say from recordings. The aired pilot, which I've seen in both full screen and side text, looks more convincingly like 2B79, and the dozen or so other episodes I was able to view (full screen) could go either way. But 2+letter is the usual pattern for the year! Is it possible an assigned 2B got mixed up and typed as 28? Any inside dirt? (And is there an 01? It seems more likely than not.)
*L.A. Firefighters ran for 6 episodes in summer 96, then was retooled and renamed Fire Co. 132 for a new 4B season which never aired, according to Wikipedia. Its article also lists the pilot as 3B99 (unusual for this period) and suggests no 3B01, but switches between code styles, and I have no broadcasts to check against.
*The Pretender was an MTM production with MTM codes, then a few episodes into season 2, the copyright page started mentioning 20thCFT instead, for most of that season anyhow. I'm going just by DVDs, which use a (later?) Fox logo starting in season 2 and may have other deviations from the original broadcasts, but the codes stay with 032 prefixes through the end of the season. For season 3, along with the new system, ABP codes were assigned.
*Secret Service Guy apparently never aired but is dated 1997. This is what epguides.com says!
*Dharma & Greg has another midseason switch, with two twists: after AE79 and AE01-18, the onscreen code switches to ABD19 and then 1ABD20-22, and of course AE is not in the 5+letter pattern (see note above). 19 seems to be the result of confusion or miscommunication. (As one of the rare exceptions to single letters gaining an AB, this was probably further complicated by the existence of 5E/ABE!)
*Two Guys, a Girl, and a Pizza Place (Two Guys and a Girl from season 3 onward) uses 5Z for its pilot (5Z79) and 5Z01-5Z09, but switches to the new format midseason, so 1ABZ10-12. It's possible that the second part of the season was not ordered at the same time as the first, but it's only 3 episodes, so possibly that production was just more amenable to a midseason switch than most others. This recoding does not change 5Z episodes that aired after 1ABZ began.

The curious case of David E. Kelley Productions

Several shows carried the 20thCFT logo, or included 20th among their copyright holders, but didn't use the typical code systems, or didn't use them entirely. A notable example, but one for which 20th had the sole copyright, is the late 90s/early 00s output of David E. Kelley productions (let's say DEK, referring to the company, not necessarily the man). DEK made a lot of shows with 20th, and yet seemed to take to this late 90s code switch oddly petulantly. Earlier shows like Picket Fences, even Chicago Hope, had normal 20th digit-letter codes under the orderly 90s system (compare also Bochco/Doogie below, also with DEK), and long after the dust had settled, The Crazy Ones in 2013 took the normal three-letter code. But over a decade in between featured a strange run of alternate codes, and a sudden midseason use of a hybrid style as if forced on DEK by 20th just like in 1966.

The grid below illustrates it succinctly. Chicago Hope (also in Table 4) is the only normal example, switching midseason from 5M to 4ABM and continuing for a few seasons with the new system. I have a hunch that the numbers prevented a characteristic DEK coding during the upcoming switch, since it couldn't fall back to 4M, and 4 with another letter would be almost as confusing. For some reason, The Practice and Ally McBeal had strange two-letter prefixes (and one inexplicable pilot number) while other 20th shows were 4_ and 5_ (though the unexplained use of AE for Dharma & Greg instead of a 5_ prefix might be related to AM).

Then when the rest of 20th had moved to three-letter codes, at least eight series got onscreen codes of a shorter hybrid style: their prefixes used the season number as a digit, then a single characteristic letter of 90s style, perhaps as a rejection of the new codes, perhaps out of confusion or lack of guidance. (79 pilots were gone, but some shows had 00 pilots instead!) Many of these conflict with older prefixes, of course (I'm looking at you, Boston Legal), even DEK's own recent Chicago Hope, with most seemingly chosen to relate to the show titles.

Meanwhile, or perhaps only retroactively, these shows did apparently have 3-letter codes (some listed officially onscreen later, or on Fox in Flight, others gleaned elsewhere on the web), all period-appropriate, and most using the forbidden letters "Q" and "U", almost as if they were dealt out for mostly-internal use, or assigned years later as some of the only available period codes.

Suddenly, in October 03, possibly in the space of a week, the short DEK codes and long 20th codes began to appear onscreen side by side, in a variety of styles, mostly but not exclusively treating the 20th ones as secondary. I've confirmed as much as I could, 8P03 to hybrid 8P04, 1H05 to hybrid 1H06, and 4B hybrid as early as 4B04. (See below for hybrid formats.) This hybrid approach, combining DEK and 20th codes (most or all using Q/U even once it was in the open!), lasted at least through the double-length finale of Boston Legal in December 08, the monumentally clumsy "Production #5F12/5F13 (5AJQ12/5AJQ13)"!

Additional code numbers and oddities

• In addition to exemplifying the "00" pilot number, Ally McBeal also uses a single code, 5M16, for one double-length episode in its final season, with no sequence gaps a la 60s series. (And episode code 2M13 is nearly obliterated by a misplaced AMPTP logo, on DVD at least!)
• The Practice's season 6 premiere is a double-length two-parter, which seems to be coded as 6P01-A and 6P01-B (other similar episodes use a single number for each part). I have not been able to check this out yet; it may be a similar case to 5M16 above.
• Boston Legal skips episode code 1F18 (1AJQ18), from all I can see.

94-96    2M, 3M Chicago Hope

96 -97

97 -98

98 -99

99 -00

00 -01

01 -02

02 -03

03 -04*

04 -05

05 -06

06 -07

20th code

Notes

4M

5M 4ABM

5ABM

6ABM

ABM

79/01+

The Practice

8402 PR

OW

3P

4P

5P

6P

7P

8P 8P/8ABQ

ABQ

01+

Ally McBeal

AM

2M

3M

4M

5M

ABU?

00/01+

Ally

??

???

Snoops

1S

ADB?

00/01+

Boston Public

1B

2B

3B

4B? 4ADU (4B)

ADU

01+

Girls Club

1G

AGA?

01+

The Brotherhood of Poland, New Hampshire

1H 1H-1AHQ

AHQ

01+?

Boston Legal

1F (1AJQ)

2F (2AJQ)

3F (3AJQ)

AJQ

01+*

The Law Firm

??

???

The Wedding Bells

1V (1AMU)

AMU

01+?

Table 5: David E. Kelley Productions and its special codes for special people.
*See descriptions above for switch boundaries. Dates: Practice 10/12-19, Poland 10/15-22, Public by 10/17 (previous ep 10/3).
*Boston Legal ran for 5 seasons, all using the same format.

Back to normal codes: a list of modern main sequence series.

Three-letter codes for new series are listed below, with the debut season, some unusual summer timings noted as needed. These are in letter sequence, not ordered by premiere date. New entries are welcome, especially for recent years. See Table 4/5 for additional codes given to transitional and DEK shows; see Fox in Flight for a few other offscreen codes.

Note that the sequence keeps its own pace and doesn't roll a letter over for a new season, though it is close to one middle letter per year. A code is assigned to a series as soon as it needs one; note the comparatively early codes for American Dad! (premiered Feb. 05, second episode in May) and The Cleveland Show, for example, which have a long lead time because they're animated.

ABK 97-98 That's Life (see oddities above) (01+)
ABR 97-98 Getting Personal (see oddities above) (01+)
ACG 98-99 Strange World (79/01+)
ACH 98-99 Holding the Baby (79/01+)
ACV 98-99 Futurama (01+)
ACW 98-99 Living in Captivity (79/01+; pilot only "1ACW-79")
ACX 98-99 Family Guy (01+; see also 1ARX01)
ADA 99-00 Roswell (79/01+)
ADC 99-00 Harsh Realm (79/01+)
ADD 99-00 Get Real (79/01+)
ADE 00-01 Dark Angel (79/01+)
ADG 99-00 Judging Amy (01+)
ADH 99-00 Angel (01+)
ADK 99-00 Titus (79/01+; all episodes hyphenated as "#ADK-##")
ADL 99-00 Then Came You
ADM 99-00 Stark Raving Mad (79/01+)
ADU 00-01 Boston Public (01+; see David E. Kelley section, e.g., "4ADU04 (4B04)")
AEA 00-01 Kate Brasher (01+)
AEB 00-01 The Lone Gunmen (79/01+)
AEF 00-01 Freakylinks
AEJ 00-01 Yes, Dear (79/01+)
AES 01-02 Reba (79/01+)
AEV 01-02 Greg the Bunny (01+)
AEW 01-02 The American Embassy
AEZ 01-02 UC: Undercover
AFB 01-02 The Education of Max Bickford
AFF 01-02 24 (79/01+; see also AZK)
AFP 01-02 Inside Schwartz
AFY 01-02 Bob Patterson (79/01+?)
AGE 02-03 Firefly (79/01+)
AGG 02-03 The Time Tunnel (only 1AGG79, unaired pilot of unsuccessful reboot)
AGH 02-03 A.U.S.A. (01+?; guides list unaired version of pilot as unlikely 0AGH01)
AGK 02-03 Still Standing (79/01+)
AGL 02-03 Charlie Lawrence (guides say 1AGL00 for first episode of 2 aired, but...)
AGS 02-03 Oliver Beene (79/01+)
AGV 02-03 The Pitts (79/01+)
AHE 03-04 Miss Match
AHJ 03-04 Still Life (never aired)
AHL 03-04 The Lyon's Den (79/01+)
AHM 03-04 Wonderfalls
AHP 03-04 Tru Calling (79/01+)
AHQ 03-04 The Brotherhood of Poland, New Hampshire (02+?; see Kelley, e.g., "1H06-1AHQ06")
AHS 03-04 Cracking Up (01+)
AHZ 03-04 The Simple Life (01+; as just 101, etc. at first, see note above)
AJA 03-04 The Big House
AJD 03-04 Arrested Development (79/01+)
AJE 03-04 North Shore
AJF 03-04 Married to the Kellys
AJN 04-05 American Dad! (01+)
AJQ 04-05 Boston Legal (01+; see David E. Kelley section, all "1F01 (1AJQ01)" etc.)
AJW 04-05 The Inside
AJX 04-05 Point Pleasant (79/01+)
AJY 04-05 Quintuplets (summer 05)
AKC 04-05 Jake in Progress
AKJ 05-06 Prison Break (79/01+; see also AZM for Resurrection/season 5)
AKK 05-06 The Loop
AKL 05-06 Over There (79/01+; summer-fall 05)
AKM 04-05 Stacked (01+) (premiered in spring 2005 but fairly early to be considered 05-06)
AKP 05-06 Head Cases (01+?)
AKT 05-06 Kitchen Confidential
AKY 05-06 Bones (79/01+)
ALF 05-06 The Unit (79/01+)
ALH 05-06 How I Met Your Mother (79/01+)
ALJ 05-06 My Name Is Earl (79/01+)
ALR 05-06 Pepper Dennis
ALW 05-06 Misconceptions (from tv.com, never aired; Wikipedia gives intended midseason date)
AMA 06-07 The Winner (79/01+)
AMB 06-07 Vanished (79/01+)
AMH 06-07 Standoff
AMK 06-07 Shark (79/01+)
AMP 06-07 Drive (01+)
AMU 06-07 The Wedding Bells (01+?; see David E. Kelley section, all "1V01 (1AMU01)" etc.)
ANJ 07-08 Journeyman
ANK 06-07 The 1/2 Hour News Hour
ANL 07-08 Unhitched
ANM 07-08 K-Ville (79/?)
ANX 07-08 Back to You (79/01+)
ANY 08-09 Life on Mars (01+) (unaired pilot unavailable, could be 79)
APK 08-09 Dollhouse (01+) (unaired pilot "Echo" 1APK79)
APS 09-10 The Cleveland Show (01+)
APT 08-09 Do Not Disturb
APW 08-09 Lie to Me (79/01+)
APX 08-09 Better Off Ted (79/01+)
ARC 09-10 Glee (79/01+)
ARG 09-10 Modern Family (79/01+)
ARK 09-10 Sons of Tucson (79/01+)
ARV 09-10 Neighbors from Hell (01+) (summer 10)
ARX 09-10 "Family Guy" Presents: Seth & Alex's Almost Live Comedy Show (only 1ARX01, special)
ARY 10-11 Raising Hope (79/01+)
ASA 10-11 Bob's Burgers (01+)
ASP 11-12 Friends with Benefits (79/01+)
AST 11-12 Napoleon Dynamite (01+)
ASW 11-12 Terra Nova (01+)
ATA 10-11 The Chicago Code (79/01+)
ATF 11-12 Don't Trust the B---- in Apartment 23 (79/01+)
ATG 11-12 Touch (79/01+)
ATM 11-12 New Girl (79/01+)
ATP 11-12 Last Man Standing (79/01+)
ATR 11-12 Awake (79/01+)
ATS 11-12 American Horror Story (79/01+)
ATT 11-12 The Finder (01+)
AVE 12-13 Ben and Kate (79/01+)
AVS 12-13 The New Normal (79/01+)
AVW 12-13 The Goodwin Games (79/01+)
AVZ 12-13 1600 Penn (79/01+)
AWL 13-14 Sleepy Hollow (79/01+)
AWM 14-15 Backstrom (79/01+)
AWN 13-14 Crisis (79/01+)
AWS 13-14 Dads (79/01+)
AWT 13-14 Friends with Better Lives (79/01+)
AWX 13-14 Back in the Game (79/01+)
AWZ 13-14 Gang Related (79/01+)
AXB 13-14 The Crazy Ones (79/01+)
AXH 15-16 Bordertown (01+)
AXP 14-15 Empire (01+)
AXT 14-15 Fresh Off the Boat (01+)
AYA 16-17 Son of Zorn (01+)
AYB 14-15 The Last Man on Earth (01+)
AYC 14-15 Cristela (01+)
AYT 15-16 Cooper Barrett's Guide to Surviving Life (01+)
AYW 15-16 The X-Files (revival; 01+; considered season 10-11 but not coded AABX/BABX)
AZH 16-17 Making History (01+)
AZK 16-17 24: Legacy (01+; clearer break from 24/AFF than some nearby examples)
AZM 16-17 Prison Break: Resurrection (01+; considered season 5 of PB, see AKJ)
AZT 16-17 The Mick (01+)
LAB 17-18 The Orville (01+)
LAL 17-18 Ghosted (01+)
LAZ 19-20 Duncanville (01+)
LBW 20-21 The Great North (01+)

Uncertain direction (20th, but change from L__ or new fork?)
DBW 21-22 Only Murders in the Building (01+)
DHW 20-21 Big Sky (01+)

Bento Box and Fox Entertainment Studios
BBDH 23-24 Krapopolis (01+)
BBGR 23-24 Grimsburg (01+)
BBHG 24-25 Universal Basic Guys (01+?)

Fox21 series
RAG 12-13 Brickleberry (01+)
VAA 04-05 Kelsey Grammer Presents: The Sketch Show (01+)
VAB 04-05 Beauty and the Geek
VAL 08-09 Game Show in My Head
VAN 06-07 The Real Wedding Crashers
WAB 08-09 Sons of Anarchy (79/01+)
WAD 10-11 Terriers (79/01+)
WAF 10-11 Breakout Kings (79/01+)
WAH 11-12 Homeland (79/01+)
WAK 13-14 Witches of East End (79/01+)
WAL 13-14 Those Who Kill (79/01+)
WAN 14-15 Legends (79/01+)
WAR 14-15 Tyrant (79/01+)
WAT 13-14 Salem (01+)
WAW 14-15 Rush (79/01+)

Other 20th/Fox-related code systems and retrocoding

Some production companies for shows distributed by 20th or related to Fox used their own coding styles, and several of those series have been brought into the modern unified system. It's worth checking them out. Because I'm not going season by season, but do want to show the ranges of codes, I list series by their full air season spans.

Steven Bochco Productions

I'll make this short. Most of these shows aired with 20thCFT logos, but the copyright was Bochco's, and the coding styles reflected a production house with no need to overcomplicate. Onscreen codes like these, particularly the all-numeric ones, can be seen in other series here and there, but this company has a few wrinkles: the later incorporation of codes into systems like Fox in Flight and the enigmatic, inconsistent use of alternate prefixes.

The numeric codes are straightforward: Bochco series number and season number (later, series letter?). They appear onscreen almost exclusively. Those alternate prefixes are variously reported as O or 0 plus a letter, with no discernible pattern to the letters (later, different first character). They appear only sparingly, and based on the official uses and onscreen examples I can find I am calling them all O. One can see why most codes avoid O and 0 entirely apart from episode numbers! (All episode numbers start at 01.) The strangest thing is that the O codes seem to be official (LOC), even when they're not onscreen, and they have less structure than the numeric ones! I've also seen them onscreen only in Capitol Critters and The Byrds of Paradise (plus one in Fox in Flight catalog, see below); elsewhere it's just the numbers, and I've confirmed that on many of these series from actual broadcasts, not just DVDs. Still, I admit the possibility that some might have aired differently. But... why? And why does FIF mix styles too? Why did NYPD Blue switch away from O; did series 8+ use up the other combining letters? Is The Practice season 2 (OW) related despite not being a Bochco series?

Note: City of Angels (99-01 seasons) is not a 20th show, but uses B1 and B2 prefixes, as if extending the series-number sequence into the alphabet. It appeared before the weirder alternate NYPD codes. That's about as much as I care to examine Bochco.

Oddities

• Season 1 of NYPD Blue shows examples of both missing and merged episode numbers: there is no 5104, and a normal-length episode is listed as 5105/5106, suggesting some dropped and combined material. The full season as aired is just 22 episodes, ending with 5124. These are slightly renumbered on FIF.
  The double-length season 9 finale is 5922 onscreen, but sometimes reported as 5922 and 5923 or 5922-A and -B, GA22-A and -B, etc.; Fox in Flight lists both parts separately yet repeats the restyled code 9ABY22 for each!

		Numeric prefixes	O_ prefixes, etc.	Notes
Doogie Howser, M.D.	89-93	11 12 13 14	??	FIF: TB11 etc.
Cop Rock	90-91	21	OX
Capitol Critters	91-92	31?	OR/ORO*	Also listed as 0173-91__
Civil Wars	91-93	41 42	OJ OL	Unavailable to check out
NYPD Blue	93-05	51 52 53 54 55 56 57 58 59 510 511 512	OK OV OG OH OT OC OE EA GA HA ?? ??	FIF: 1ABY etc.
The Byrds of Paradise	93-94	61?	OP
Murder One	95-97	71 72 (7223-35 odd*)	ON OU (OU11-18*)	FIF: TAON (only)

Table 6: Steven Bochco Productions (first seven series, with 20th).
*Capitol Critters codes onscreen really push the O/0 confusion, with the first 9 episodes apparently typeset as ORO1 to ORO9 (I can only find 9 and above); it's not the first time a leading 0 in a two-digit episode number was typeset as an O, yet both characters seem to clearly be Os and not 0s. Then comes OR12 (normal), but ORO 11 (with a space) and ORO10, suggesting it took two episodes in production order for someone to realize it wasn't ORO+number! Wikipedia lists them all as ORO.
*The last eight episodes of Murder One aired in pairs on four dates, and on DVD they are presented as four continuous double-length episodes, with onscreen codes 7223 to 7235 (odd numbers only), rather than, for example, 7211/7212. Episode lists that use O codes say OU11-OU18; I do not know how the show originally aired, perhaps separate back-to-back episodes with single codes 7211, 7212, etc., or even the O codes.

Fox Television Studios (etc.)

For over a decade (a sign of quality), and starting at about the same time as 20thCFT's revamped three-letter system, a very good system was in use at Fox Television Studios, though I am fairly partial to post-60s 20th styles because the letters really help avoid ambiguity. Codes combined three sections separated by hyphens: a sequential series number (or pilot sequence), a two-digit date (start of production year), and a three-digit season/episode number (179 for pilot, 101, etc.). Even the best 20th codes miss one of those details, and FTS codes even highlight how some pilots are made the previous year. Consistency was a little low, with some series skipping a separate pilot sequence designation, others using that for the full first season. The series number seems nice and orderly, even when "50"s started appearing at the start of all of them, but it's possible there are two concurrent sequences going, especially since 5012 not only conflicts with 12 but predates it by several years. (Alignment of B and A/C codes as seen below supports the existence of 2 or more sequences/subcompanies. Not all of these shows identify Fox Television Studios by logo or copyright, though Wikipedia seems to lump them under it.)

Suddenly, in 2011, these long but descriptive code triads were abandoned in favor of a more compact system for onscreen use, one very close to 20th's own except for one detail. Each series got a three-letter code (some or all of which had been assigned years before, judging from Fox in Flight catalogs of 2008), and used it plus the season and episode number from then on, except that the series code came first. Why was it BCI501 and not 5BCI01? (Why is the letter I allowed, along with U and perhaps more?) Did this sequence and others prevent the 20thCFT rollover from A to B?

As early as 2007, some (although not all) series supplemented the official production code with what I think is meant to be an air order season-episode number preceded by an "S". (79s, or 179s, often didn't have those, but counting with episode number 01 began after the pilot.) This could also be a mouthful, especially in double-length episodes, such as Burn Notice's season 1 finale (episodes 11 and 12, or one long 11), which is declared "Production: # 5037-07-110/111/S110/S111". Several series, noted in the footnote below, use S codes that are not in air order, so perhaps they do mean something else.

The grid below includes three-letter codes for series that did not use them onscreen, pulled from the Fox in Flight catalog. Again, these may have been assigned when the shows were new, or well before 2008. It also lists some examples of the S codes. Lights Out aired right on the cusp of the format change, after some later-in-sequence series' full seasons, but I've been unable to examine it to see what system it uses; it could go either way.

In 2014, Fox Television Studios merged with Fox21 (see WA_ codes above) into Fox 21 Television Studios, though the shows I've looked at did not all switch logos immediately, and all kept their code styles. More recent history is a topic of future examination.

		Up to 10-11	11-12 and later/ Alt code	Notes and S-style examples
The Hughleys	98-02	2-98-179/101+ 2-99-201+ 2-00-301+ 2-01-401+	AAB
Oh Grow Up	99-00	10011-99-179 04-99-101+
Malcolm in the Middle	99-06	10012-99-179 06-99-101+ ... 06-05-701+	CAB
The Bernie Mac Show	01-06	10041-01-179 08-01-101+ 08-02-201+ ... 08-05-501+	CAS
The Shield	01-08	5012-01-179/101+ 5012-02-201+ ... 5012-06-601+ 5012-07-701+
Listen Up	04-05	10068-04-179 12-04-101+
Living with Fran	04-06	13-04-179/101+ 12-05-201+*	CBR	S2 "12" typo?*
The Riches	06-08	10095-06-179/101+ 5034-07-201+	BCF
Burn Notice	07-14	10105-06-179 5037-07-101+ ... 5037-10-401+	BCI501+ BCI601+ BCI701+	No extra pilot code 5037-07-102/S101 BCI501/S501
White Collar	09-15	5039-08-179 5039-09-101+ 5039-10-201+	BCW301+ BCW401+ BCW501+ BCW601+	No extra pilot code 5039-09-103/S103* BCW301/S301*
Lights Out	10-11	???/only BDA?	BDA, 179/101+	Debuted after BDE/BDF S1
The Good Guys	10-11	5042-10-101+	BDE	5042-10-113 /S113; no 179?
The Glades	10-14	5046-09-179 5046-10-101+	BDF201+ BDF301+ BDF401+	No extra pilot code 5046-09-101/S101* BDF201/S201
The Killing	10-14		BDH179/101+ BDH201+ BDH301+ BDH401+	BDH179/S179 BDH101/S101
The Americans	12-18		BDU179/101+ BDU201+ ... BDU601+	BDU179/S179 BDU101/S101 As Fox21 TS for S3+
Graceland	13-16		BDV179/101+ BDV201+ BDV301+	BDV179/S179 BDV101/S101 (+205-213) BDV201/s201 (to 204) BDV301; S3 as Fox21 TS
Sirens	13-15		BDZ179/101+ BDZ201+	No extra pilot code BDZ101/S101*
The Comedians	14-15		BEF179/101+	No S codes; as Fox21 TS

Table 7: Fox Television Studios and cutover in brief.
* Season 2 of Living with Fran clearly shows its series code as 12, but it should be 13 (and 12 conflicts with Listen Up, or would, if that had gotten a second season. How'd that happen?
*The S-style codes for White Collar and season 1 of The Glades do not follow the air or production order; apart from being off by one for a pilot, other shows' codes are in air order. Do they mean something else, did producers expect another air order, or what? And Sirens (season 1, I haven't inspected 2) uses S codes weirdly and redundantly matching the production codes.

Fox in Flight, iTunes, etc.: rewriting history

With a broad catalog of series across the Fox brands, including decades-old ones and series acquired from other companies, all with a mismatched and often conflicting set of production codes, the company had some work to do to offer series for licensing and direct consumer purchase through online marketplaces. All of the research I've done has been based on the "Fox in Flight" page, an online catalog (c. 2007-16) that I think was meant to let airlines select what it would license to offer as in-flight entertainment (perhaps as linear programming or episode-name-only interfaces, the production codes likely for internal use); I am told the codes below are or were used on places like AOL Video and iTunes, too, but have not investigated much further or sought out more recent examples. The idea is to show a curious slightly-inside look at the industry and how it adapted the codes, and I thank Brian for this pointer.

The Fox in Flight choices, last seen in 2016, are available here. Many offerings are a curious subset of seasons or episodes, with random omissions and sometimes just a few episodes available at all. A number of double-length two-parters are offered as separate episodes (with their own single codes), but perhaps they could only be licensed and viewed as pairs. And some of the adapted episode code lists take major liberties with the two-digit episode numbers (I can't list them all). This is also where some margin-dwelling 20th shows' codes are revealed, with a few twists, and a good deal of fairly intuitive 90s code backnumbering. Most notable for this document: 3G episodes of The Simpsons, rather than being adapted into the 7ABF range, make rare use of the letter "I", becoming 7ABI01-04.

Based on the selection on FIF, I have made these categorizations.

• Shows using the existing 3-letter codes for all of their episodes are listed that way. This includes all normal A__ codes and Fox21 WA_ codes, the internal A__ codes for pertinent Kelley shows that double-coded (Boston Public, Boston Legal), and Martial Law (semi-20th with no onscreen codes, began 98-99, ACU) in air order, FIF being the only official place I've seen the ACU code although perhaps it was used internally. These total in the dozens.

• Shows that straddled the boundary from the 90s or outside styles to the new system back-number the older episodes accordingly (Simpsons 7G = 1ABF, 7F = 2ABF, etc.; 3Gs become 7ABIs under this style and 31-33s are not renumbered). This includes relevant double-coded Kelley shows (Chicago Hope, The Practice now with pilot 1ABQ79), The Pretender (severely renumbered, into air order?), and NYPD Blue (see Bochco notes) with code ABY and some renumbering.

• Older shows with 4-character alphanumeric codes that didn't stretch into the new system tack "TA" or "TB" onto the front, though some shows used codes from alternative systems, including non-onscreen variants. Hyphens and part numbers are omitted. For some reason, Daniel Boone seasons 1 to 3 are the bare 4-digit codes in these listings, but may be intended as TA+code; season 5 has TA and seasons 4 and 6 just aren't listed. The TA/TB system seems designed to avoid overlaps (note all TAs are of different letter-number patterns, both TBs...), although actually none of the offerings of these six shows do overlap (Daniel Boone and Doogie Howser's season 4s would, but aren't in the catalog!). Note that the TA prefixes did not prevent The Simpsons from using TABF codes.
  
  TA:
  The Green Hornet (TA9801 etc., renumbers/flattens 2-parter codes)
  The Paper Chase (TAT701 etc.; original season only, no pilot)
  L.A. Law (TA4L01 etc.)
  Murder One (TAON01 etc., not TA7101 onscreen style; no season 2)
  Daniel Boone (no TA on first 3 seasons, 7426 2-parter one entry; season 5 TA3001 etc.)

  TB:
  M*A*S*H (TBJ305 etc., double length episodes listed separately; no pilot)
  Doogie Howser, M.D. (TB1113 etc.)

• Shows from other recent Fox spinoff brands like FTS and FX use a three-letter prefix and then 3-digit season-episode code, perhaps deviating from the usual component order to match the FTS one. FTS prefixes are orderly despite not appearing onscreen until 2011, with lots of them listed on FIF as early as 2008 as well, suggesting they had these codes somewhere official for years. The first letters A-D might classify the shows by co-production companies. For FTS shows before 2011, the codes are backnumbered, including using 179s for pilots.

  AAB### 98-02 The Hughleys
  
  BCF### 06-08 The Riches
  BCI### 07-14 Burn Notice
  BCW### 09-15 White Collar
  BDA### 10-11 Lights Out
  BDE### 10-11 The Good Guys (no 79)
  BDF### 10-14 The Glades
  BDH### 10-14 The Killing
  BDU### 12-18 The Americans (Fox21 TS for season 3 up)
  BDV### 13-16 Graceland
  BDZ### 13-15 Sirens
  BEF### 14-15 The Comedians (Fox21 TS)
  
  CAB### 99-06 Malcolm in the Middle
  CAS### 01-06 The Bernie Mac Show
  CBR### 04-06 Living with Fran
  CBW### 05-06 Killer Instinct
  
  DDZ### 08-12 Kendra (no onscreen codes; no 79; 50 and 51 codes not seen elsewhere)
  

  FX/FXP shows (using a lengthy but fairly straightforward onscreen style) drop their native codes and get YB_ and YJ_ codes instead (sequential vs. hand-picked FX digraphs?); the strangest thing by far is that for It's Always Sunny in Philadelphia, besides severely renumbering some episodes, it eschews the alphanumeric season codes in favor of a new prefix! The list below includes the FX "X" prefixes for comparison (prior to 2010 there was no X; "x" stands for transitional series). These shows all start at 101.

  YBP### 05-14 xIP It's Always Sunny in Philadelphia (season 1-9) (Xmas = 597)
  YBY### 14-   XIP It's Always Sunny in Philadelphia (season 10 YBY101+, 11 YBY201+, +?)
  
  YJE### 09-16 xLE The League
  YJF### 10-15 XCK Louie
  YJH### 11-14 XWL Wilfred (all firmly summer airdates)
  YJX### 14-19 XYW You're the Worst
  YJZ### 14-   XFO Fargo
  

• Old shows from MTM Enterprises/Productions (which 20thCFT acquired) use a similar 3-letter format, but with YA_ codes instead (not entirely chronological). These shows tended to have 4-digit codes a little like 20th's 60s style, complete with separate pilot codes, but repeated their first 2 digits quite a lot. They also skipped over episode numbers very often, and the original designations are generally reflected here except for the pilots. (Actually, the older MTM shows had an extra first 4 digits corresponding to the series, pilots even more, but those aren't important here.)
  
  YAD 78-82 WKRP in Cincinnati (pilot 1YAD68, may be renumbered, no onscreen codes)
  YAL 80-87 Hill Street Blues (pilot 1YAL25, 2-parters ...13A/13B/14A/14B now 1YAL13-16)
  YAM 82-87 Remington Steele (pilot 1YAM79)
  YAN 70-77 The Mary Tyler Moore Show (no separate pilot code)
  YAU 82-90 Newhart (pilot 1YAU79)

• Brian reported DYO for Dynasty (1DYO01, etc.), another rare use of "O", but listings are not on FIF archives.

FIF is not the only place where alternative code formats could be seen, but I haven't seen many lately, primarily air season/episode combinations (#-##, #x##, S#E##) that have nothing to do with production codes. When I began this guide, some online TV guides used the 4-character Simpsons codes when available but then (also 4-character) adaptations for the "ABF" years. AABF01 became 1001, and so on, matching their simpler production code listings of other series.
Other people may use production codes in hotel-room format casually when the series itself is known, for example, in discussing Futurama, "410" for 4ACV10. This doesn't work too well for 90s Simpsons without backnumbering or past season 34 but I will make shorthand notes for Simpsons F23 or American Dad! G09, etc.

Non-20thCFT styles for comparison and interest

Other production companies, of course, have different methods. Many are purely numeric and consist of the same room-numbering sort of system: 101 is season 1, episode 1, etc., and these don't tend to appear onscreen. Others have special prefixes that do appear in the credits; MTM is one I might chart out in the future, along with expanding the section below, but until that time, I leave you with the WB info roughly as it looked in 2009 (it's just gotten weirder since then). If you spy a code in another company's show, dive down that rabbit hole!

Warner Brothers TV, Lorimar, etc.

These shows have a similar set of evolving codes, special pilot sequences, etc. For full seasons, chunks of 50 numbers are assigned, so episodes tend to start at 01 or 51; shows do not have their own special prefixes from season to season. Codes seem to use "A" and "B" after the same number to denote two-parters, instead of entirely different numbers. The samples below are incomplete for now, not as thoroughly vetted, but illustrative, with the first number from each chunk. Italics represent pilots, when separate numbers exist and are known.

	Per- fect Stran- gers	Full House	[Guns of] Para- dise	Family Mat- ters	Gab- riel's Fire	DEA	The Fresh Prince of Bel- Air	Sis- ters	Home- front	Step by Step	ER
85-86	174901
86-87	175501
87-88	176501	??????
88-89	177507 to 526 445227 445228	??????	187101 to 112 445463 to 476
89-90	445751	445851	445951	445230 446001
90-91	446301	??????	446701	446451	475034 446601	475035 446651	446801	475039 446751
91-92	446851	446951		446901	447301		446901*	447251	447151	475049 447001
92-93	447951	447851		447801			446951*	447651	447701	447901
93-94		??????		455351			alt #s	455851		455451
94-95		??????		456201			alt #s	456501		456351	475079 456601
95-96				457101			alt #s	457001		457151	457201
96-97				465301						465351	465401
97-98				466451						466501	466351
98-99											467551
99-00											225451
00-01											226251

*The Fresh Prince of Bel-Air numbers start as if they're in sequence with the rest but season 2 and 3 step on other series' allotted numbers. Its last three seasons are listed online with completely different numbers. It may not belong with these series!

ER

Small- ville

Cold Case

Nip/ Tuck

One Tree Hill

Super- natu- ral

T. New Adv. of Old Chris- tine

Chuck

Push- ing Dais- ies

The Big Bang Theory

Gossip Girl

Moon- Light

Termi- nator: TSCC

01-02

227251

475165 227601

02-03

175151

175051

03-04

176001

176201

475195 176701

475194 176451

475360 177501

04-05

177851

2T5201

177751

177601

2T5251

05-06

2T6051

2T6401

2T6351

2T5951

2T6151

475285 2T6901

475297 2T7451

06-07

2T7801

2T7701

2T7901

3T5001

3T5751

3T5501

3T5551

07-08

3T6151

3T6301

??????

3T6401

3T6801

3T6901

3T6701

276025 3T6451

276027 3T6501

276023 3T6601

276026 3T6751

?????? 3T6951

276022 3T6851

08-09

3T7101

3T7451

??????

3T7551

3T7501

3T7851

3T7251

3T7051

3T7351

??????

3T7301

09-10

3X5251

??????

3T7901

3X5301

3X5201

3X5601

3X5801

3X5551

??????

10-11

3X6001

3X6351

3X6051

3X6301

3X6651

??????

11-12

3X7201

3X7051 ...

3X6751

3X6851 ...

?????? ...

As this jumps around, there still manage to be some overlaps, for example, Perfect Strangers 88-89 and One Tree Hill 03-04. Whether WB and Lorimar shared codes or just happened to interleave very similar ones is another future question.

Wishlist

I'd love to fill in some gaps in the 20thCFT codes, especially in the older, wilder decades. Many series are hard to find, officially or not, and particularly for the ones that survive only in studio vaults and home recordings, maybe I can inspire someone to dust off an old tape. Please let me know if you have any leads, new information, corrections, etc.!

Some especially desired stuff (along with anything I've expressed doubt about):

• Hagen (entire series), more than scraps of info about That's Hollywood
• First episodes (air and/or production) of series such as Karen, Roll Out!, Trauma Center; several exist online but are missing codes
• Nanny and the Professor season 1, more of Judd for the Defense
• Better copies of pilots with blurry codes
• Dead on Target, failed (Our Man/In Like) Flint pilot, is on DVD but with audio-only credits!
• Confirmation of midseason code switches, as aired, in Chicago Hope, Boston Public, etc.
• How codes appeared in The Simple Life seasons 2, 3, and 5 (even 1, which may differ from DVD)
• Other format anomalies (lack of hyphens, etc.) in Masquerade, Cover Up...

Hall of fame

We end with one more look at 20thCFT's modern era. The consistency of those codes made year-by-year grids unnecessary, but I'd like to highlight series that broke into the alphanumeric season characters. (Some of them even spell words: BATS and CATS for AHS seem appropriately spooky!)

This includes only those natively part of the system, with codes like this onscreen, so no M*A*S*H, no NYPD Blue (even if it would be coded BABY, tee hee); also, sorry, The X-Files, going from 9ABX to 1AYW/2AYW disqualifies you! It's quite possible that I've missed some, so please let me know of any oversights.

The hall of fame as of September 2024, by highest prefix/number of production seasons, not necessarily by air seasons or episode count:

Series		Code			# of seasons
Modern Family		BARG			11
Bones		CAKY			12
American Horror Story		CATS			12 and counting
King of the Hill		DABE			13
Bob's Burgers		DASA			13 and counting
American Dad!		HAJN			17 and counting
Family Guy (skipped GACX)		NACX			21 and counting
The Simpsons (used up alphabet)		35ABF			35 ...and counting!