History Main / EpisodeCodeNumber

{{Pilot}} episodes usually aren't given a code, although some have a "season 1" code with an out-of-sequence episode number like 00, 99 or 79 (a strange yet surprisingly common number for pilots). Pilots with no code may be retroactively labeled "episode 0" for the sake of consistency.

* ''Series/DoctorWho'' used an increasing number of letters from Seasons 1-26 (A-Z, then AA/BB/etc. and later 4C, 7D, etc.), then Seasonal Numbering with the revival. [[http://www.drwho-online.co.uk/episodes/doctorwho/episodes-doctorwho.aspx A list is here.]] Note the three codes for ''The Trial of a Time Lord'' — that 14-part story is effectively made up of four separate chunks (''The Mysterious Planet'', ''Mindwarp'', ''Terror of the Vervoids'', and ''The Ultimate Foe''), with the last two produced together as a single block and sharing a code (7C). Also notice that the codes for some Season 30 (Series 4) episodes don't match the broadcast order — this isn't a case of ExecutiveMeddling, but of the show's creators altering the plot as the season was being filmed; they kept the original codes to avoid confusion.
** According to the BBC, the current run of ''Series/DoctorWho'' is not the same as the old run, thus the Tenth Doctor ended his tenure in "''Doctor Who'' (2005) Series 4".
** Big Finish gives the production code "8A" to the 1996 film, and their ''Who'' audio dramas with Paul [=McGann=] continue the numbering as you'd expect (8B, 8C...).
** The codes skips some letters if the production team of the time thought could be confused for other letters or numbers, althought inevitably, this is inconsistent. One spin-off short story was written as the paratext for the {{Uninstallment}} Serial I, between "Reign of Terror" and "Planet of the Giants".

** At least the 1971 pilot of ''Series/SplitSecond1972'' used "SPS"; it's not certain what the series used.

* Creator/{{Konami}} used production codenames for their games in the late 80s and early 90s, and it's common to see the codes inserted into games of that era as a DevelopmentGag. ''VideoGame/MetalGear'' was N313, which is also the codename for Solid Snake's infiltration mission into Outer Heaven; ''VideoGame/{{Gradius}} 2'' was N322, and your ship is an N322 Starfighter.

* While not the official codes, ''Anime/PokemonTheSeries'' episodes are among the fandom generally assigned a two-letter prefix (EP, AG, DP, BW, XY, SM, JN, HZ, or SS) followed by a three-digit episode number. "[=EP038=]", for example, is the 38th episode of the original series ("[[MissingEpisode Electric Soldier Porygon]]"). "[=AG049=]" refers to the 49th episode of the ''[[Anime/PokemonTheSeriesRubyAndSapphire Advanced Generation]]'' series, and so on. "DP" refers to the ''[[Anime/PokemonTheSeriesDiamondAndPearl Diamond & Pearl]]'' series, "BW" to the ''[[Anime/PokemonTheSeriesBlackAndWhite Black & White]]'' series, "XY" to the ''[[Anime/PokemonTheSeriesXY XY]]'' series, "SM" to ''[[Anime/PokemonTheSeriesSunAndMoon Sun & Moon]]'' series, "JN" to ''[[Anime/PokemonJourneysTheSeries Journeys]]'' series, "HZ" to ''[[Anime/PokemonHorizonsTheSeries Horizons]]'' series, and "SS" to the "side-story" episodes occasionally shown on ''Weekly Pokémon Broadcasting Station'' or ''Pokémon Sunday'', dubbed under the ''[[Anime/PokemonChronicles Pokémon Chronicles]]'' banner or as individual specials. The movies are designated with an M followed by a two-digit number ("[=M01=]" being...well, ''The First Movie''), and a small handful of episodes do not have codes as a result of being aired OutOfOrder. [[TheWikiRule Bulbapedia]] has this pretty much standardized and refers to them as [[http://bulbapedia.bulbagarden.net/wiki/Bulbapedia:Epicode epicodes]].

* While not the official codes, ''Anime/{{Pokemon}}'' episodes are among the fandom generally assigned a two-letter prefix (EP, AG, DP, BW, XY, or SS) followed by a three-digit episode number. "[=EP038=]", for example, is the 38th episode of the original series ("[[MissingEpisode Electric Soldier Porygon]]"). "[=AG049=]" refers to the 49th episode of the ''Advanced Generation'' series, and so on. "DP" refers to the ''Diamond & Pearl'' series, "BW" to the ''Black & White'' series, "XY" to the ''XY'' series, and "SS" to the "side-story" episodes occasionally shown on ''Weekly Pokémon Broadcasting Station'' or ''Pokémon Sunday'', dubbed under the ''Pokémon Chronicles'' banner or as individual specials. The movies are designated with an M followed by a two-digit number ("[=M01=]" being...well, ''The First Movie''), and a small handful of episodes do not have codes as a result of being aired OutOfOrder. [[TheWikiRule Bulbapedia]] has this pretty much standardized and refers to them as [[http://bulbapedia.bulbagarden.net/wiki/Bulbapedia:Epicode epicodes]].

** The current system, adopted in 1997-98, uses a four-character prefix where the first one is the season number (''The Simpsons'' uses letters since it was already [[LongRunners above nine seasons]] at the time of the switch [[note]]The letter "I" was never used, while "O", "Q" and "U" were skipped at first, but with "Z" being reached in 2020, "Q", "U" and "O" have been used for seasons 32 to 34. With them officially running out of letters in 2023, episodes for seasons 35 onward will have the season's number instead of a letter (35ABFxx).[[/note]]) and the remaining three is the series code pulled from an alphabetical sequence, such as "ACX" for ''WesternAnimation/FamilyGuy'' or "ACV" for ''WesternAnimation/{{Futurama}}''. Series previously under the old system had "AB" added to their existing letter (e.g. "F" became "ABF"); "AA_" codes were never used. Due to the complicated-looking codes this system produces, simplifications have sometimes been made, such as some online TV guides coding ''The Simpsons'' episodes past Season 9 with a simple season-episode number (e.g. [=CABF06=] becomes 1206) or David X. Cohen dropping the "ACV" when referring to ''Futurama'' episodes (e.g. 4ACV10 becomes 410).

** The current system, adopted in 1997-98, uses a four-character prefix where the first one is the season number (''The Simpsons'' uses letters since it was already [[LongRunners above nine seasons]] at the time of the switch [[note]]The letters "I", "O", "Q" and "U" were skipped at first, but with "Z" being reached in 2020, "Q", "U" and "O" have been used for seasons 32 to 34. With them officially running out of letters in 2023, episodes for seasons 35 onward will have the season's number instead of a letter (35ABFxx).[[/note]]) and the remaining three is the series code pulled from an alphabetical sequence, such as "ACX" for ''WesternAnimation/FamilyGuy'' or "ACV" for ''WesternAnimation/{{Futurama}}''. Series previously under the old system had "AB" added to their existing letter (e.g. "F" became "ABF"); "AA_" codes were never used. Due to the complicated-looking codes this system produces, simplifications have sometimes been made, such as some online TV guides coding ''The Simpsons'' episodes past Season 9 with a simple season-episode number (e.g. [=CABF06=] becomes 1206) or David X. Cohen dropping the "ACV" when referring to ''Futurama'' episodes (e.g. 4ACV10 becomes 410).

** The current system, adopted in 1997-98, uses a four-character prefix where the first one is the season number (''The Simpsons'' uses letters since it was already [[LongRunners above nine seasons]] at the time of the switch [[note]][the letters "I", "O", "Q" and "U" were skipped at first, but with "Z" being reached in 2020, "Q" will be used next and the other skipped letters may or may not be used as they figure out how to keep the code going][[/note]]) and the remaining three is the series code pulled from an alphabetical sequence, such as "ACX" for ''WesternAnimation/FamilyGuy'' or "ACV" for ''WesternAnimation/{{Futurama}}''. Series previously under the old system had "AB" added to their existing letter (e.g. "F" became "ABF"); "AA_" codes were never used. Due to the complicated-looking codes this system produces, simplifications have sometimes been made, such as some online TV guides coding ''The Simpsons'' episodes past Season 9 with a simple season-episode number (e.g. [=CABF06=] becomes 1206) or David X. Cohen dropping the "ACV" when referring to ''Futurama'' episodes (e.g. 4ACV10 becomes 410).