[[quoteright:300:[[Franchise/SailorMoon http://static.tvtropes.org/pmwiki/pub/images/sailorearth.png]]]]
[[caption-width-right:300:[[http://pookah-sama.deviantart.com/ Original character!]] [[MemeticMutation Donut steel!]]]]
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->''"If an NPC is known as 'the One', I cannot volunteer to be 'the Two'."''
-->-- ''Blog/ThingsMrWelchIsNoLongerAllowedToDoInAnRPG''

In stories where the [[GeodesicCast characters are organized]] with a kind of official order, hierarchy, or theme it becomes easy to simply expand that group to add new characters of the same type. This means the writer doesn't have to {{retcon}} half the {{backstory}} in order to add additional characters to the cast. Likewise, well-done [[FanFiction fanfics]] can use the same principle to insert original characters, bending {{canon}} instead of breaking it. If this is done to [[CousinOliver simply add a new character out of the blue]], it can give the illusion of added legitimacy to the new character's [[SixthRanger place within the hierarchy/theme]] of the cast. If the main characters are the last of their kind, then these characters will be ThereIsAnother.

Unfortunately, {{Mary Sue}}s appearing as {{Original Character}}s in SelfInsertFic using this trope are common enough that some fandoms have a knee-jerk hatred of them. Especially when the trope is used to rehash ideas for a role that has already been filled in canon or previous fanfics. However, TropesAreNotBad and it can still be used legitimately.

Named for a particularly prevalent phenomenon in ''Franchise/SailorMoon'' fiction.

See also: SendInTheClones, ElsewhereFic. Compare ObviousCrossoverMethod. If a character of this type becomes {{Mary Sue}}ified, and then overhauled with more power than the canon should give them and then some, it becomes a CopyCatSue. See also TheUnChosenOne. Not to be confused with the webcomic ''Webcomic/SailorSun''.

'''Please''' do not add personal examples of this to the page. This is discussing general trends of the trope or particularly notable examples.

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[[foldercontrol]]

!!Examples

[[folder:General]]
* Pretty much ''any'' series with a school/classroom setting will have hundreds of fics introducing a NewTransferStudent, and a smaller but still significant number introducing a new teacher, often an [[NextGenFic aged-up original cast member]] or [[{{Crossover}} someone from a different series]].
* {{Space Opera}}s make it quite easy to introduce another spaceship with a captain and, perhaps, a full crew, though unlike most examples, this is, by definition, ''very'' reasonable.
* Any series set in a military environment can easily accommodate team changes that ensure a steady influx of new fan characters.
* Similarly, hospital dramas can always add new nurses and interns.
* Any series where the characters are defined and symbolized by an object of a specific theme, such as fruits or animals. Creating new characters in such universes are as easy as copy-and-pasting a basic template then just throwing in the key character traits of your choice (which in fact many people do to create their [=OCs=]).
* Any work that involves a position or title being passed from generation to generation will have characters being past or even future bearers of the title.
[[/folder]]

[[folder:Anime & Manga]]
* Any hypothetical Sailor Soldier in ''Franchise/SailorMoon'', but especially the obviously missing "Sailor Earth" (whose role is technically filled by Usagi's boyfriend [[note]]Mamoru/Endymion has what would be the Sailor Crystal of Earth, however the rule is that only girls can be Sailor Senshi, so this makes him the closest to a canonical Sailor Earth.[[/note]]). The manga's creator later admits that none of the later senshi were actually planned out before they appeared, since the series was initially intended to only feature the few girls to follow the FiveManBand rule; the "every planet could have a senshi" ShrugOfGod eventually became canonical and used frequently in the anime and especially musicals.
** An early appearance by a Sailor ''Pluto'' rather than a ''Saturn'' just fueled the early speculation there should be senshi for three leftover planets; {{fanon}} versions of them existed before canon versions.
** After the ''Sailor Moon'' [[Anime/SailorMoon anime]], whose {{sentai}} ascendants were likely to have literal {{Sixth Ranger}}s, magical girl shows needing filler usually have an easy mnemonic for adding new characters when needed.
** Note that pretty much any astronomical object tends to get Senshi[[note]]though it's not likely anyone is going to make a Sailor 99942 Apophis or a Sailor 47 Ursae Majoris b[[/note]], and this was going on ''well'' before Pluto was demoted from planetary status. The series itself was mum on where the Sailor Starlights actually got their Sailor Crystals from (though the anime implied through a flashback they may have been representing moons of the planet Kinmoku), and Sailor ''Cosmos'' isn't helping any. Stars are extremely common targets for fan Senshi, the most prominent continuing to be creating a Sailor Sun (aka Sailor Solaris if you're being technical). Also, there's precedent for galaxies to get them if you ''really'' want a Mary Sue.
** What's annoying is that many of the fan senshi do not stray too far outside the box. Although the Senshi's fuku, or uniforms, are shown to be vastly different around the galaxy with only the Sailor collar being the always present component (compare the Starlights and the Solar System Senshi), many OC creators tend to stick with the Sol Senshi uniform formula despite their being little to no evidence of Senshi elsewhere have similar uniforms.
** This trope also applies to villains, as the series employed largely gem or mineral based theme names to each villain group, with a slight tweak for themes. Thus, most fanfic villain groups find themselves named after whatever collection of gems or minerals the author thinks is menacing enough. Double points if that gem or mineral ends with "-ite" (common examples being "Quartzite" or "Pyrite") and triple points if they're a missing King (often mislabeled "General") from the first series.
** A big irony about the Sailor Earth phenomenon in this canon is that there ''is'' a canon Sailor Earth and (technically) Sailor Sun. Even if [[spoiler: one of them's a guy and one of them represents the BigBad,]] there's no actual fanon need for ''either'' to exist.
* ''Manga/DragonBall'' fanfiction loves to introduce previously unknown members of Goku or Vegeta's family, like a long-lost sister or a half-whatever-hybrid left behind during the Saiyajin wars of conquest; forgotten childhood friends are another popular one. Ditto Namekians. Additional Cyborgs aren't as popular, since the WordOfGod has listed all of Dr. Gero's known creations, but this doesn't stop some from appending more onto the list.
** Incidentally, Vegeta having a long lost sibling became AscendedFanon -- see the 2008 special.
** Lunch has a sheer amount of [[AlwaysFemale daughters]] that always go along really well with Goten and/or Trunks.
** Speaking of Trunks, another popular theme is to have Goku and Chi Chi have a daughter and have her hook up with him.
*** Sometimes it's Gohan and Videl's daughter, Pan or a self-inserted Mary Sue.
** Given that the Saiyans are established to have regularly been sent all over the universe for conquest (and Goku being sent as an infant was not an unusual case), the idea that one more could've slipped through the cracks of Freeza's massacre is quite plausible. That it would happen to be a member of the royal family? A bit less so. And yet... again, see the 2008 special.
* Any number of new Nth Children in ''Anime/NeonGenesisEvangelion''. Nth Angels where N is greater than 17 also crop up in {{Continuation}}s whose authors either ignore both endings of the series or is going for an AlternateUniverseFic. Rebuild doesn't help this, since it ''re''numbered the Angels, added new ones and removing old ones.
** Oh, and let us not forget Eva Unit N whose major difference from the others will be production country, color scheme and placement of (any) horns. Fans are divided on whether ''Evangelion Rebuild'' is [[EpilepticTrees canonizing or deconstructing]] this trend with Mari. The fact that Rebuild provides us with five additional Evas, but numbers them in a way that leaves room for four more (07, 10, 11, and 12) doesn't help matters.
* In the ''RozenMaiden'' anime, there is another dollmaker named Enju, who only made one doll. He is often seen as a plot device with which to bring in more dolls without affecting the ''Rozen Maiden'' lineup.
* ''TokyoMewMew'' makes this easy; there's an almost infinite amount of [[ThemeNaming sweet foods]] and a lot of endangered animals.
* Since only a small fraction of the seated [[TheGrimReaper shinigami]] officers of ''Manga/{{Bleach}}'' have been revealed in the {{canon}}, it's easy to introduce new characters, especially in the less-known divisions like the first, the seventh, and the tenth.
** This also applies to the numbered Arrancar. 110 of them exist, but only about 20 of them have been shown, much less named. The novel ''Bleach: Spirits Are Forever With You'' by Ryohgo Narita takes full advantage of this.
** There are also the rare Visored Sailor Earth, Quincies who thought ''they'' were the last of their kind before meeting Uryuu, humans like Chad, or other types such as variations of Quincy Powers (Since there's an entire world to explore and [[FillerVillain Bounts]] could possibly not be the only spiritually-aware humans), or other types of people with Kido-shinigami powers like Orihime and Hachi. Of course; these people are often very rare - possibly because these types are often rather harder to do than simply naming one-self as a seated officer or Arrancar who wasn't introduced.
** Rarely, one may actually have a Bount who ''wasn't'' rounded up by Kariya.
** May also apply to Uryuu -- when he was introduced, it turns out he had been in Ichigo's class the entire time. Ichigo just didn't recognize the name.
** The extreme ease (in both canon and filler) at which it seems ''anybody'' (regardless of whether they appear to be obviously the wrong age) can transfer into Ichigo & company's high school makes it that much simpler to introduce such an OC into the main characters' circle of friends.
** ''Bleach'' fanfic writers also tend to enjoy adding in a "14th Division", which allows them to make their OC a captain without killing off any of the existing ones. Oddly enough the Kido Corps (which was revealed in the Turn Back the Pendulum arc to be something akin to a "14th Division" in canon) rarely gets used, even though its missing Captain and Lieutenant never had canonical replacements introduced, ''none'' of its current membership have ever been named or even had their faces revealed, and the Corps has a secretive nature that gives writers a blank check for its inner workings.
** And now there are Fullbrings, humans who can have pretty much any power because their mothers were attacked by hollows while they were pregnant with them. This is pretty much a blank check for any fanfic writers.
** The final arc introduces the Vandenreich who are revealed to be [[spoiler: Quincies]]. Their powers are far more diverse than what we had seen of [[spoiler: Quincies so far]], which opens up fan fic writers to think of their own abilities.
* In ''FruitsBasket'' fic, there is the 'wolf of the zodiac' story. Despite the fact that the EasternZodiac only has 12 slots, with the cat added from tradition, many ficcers will add in another animal, usually a wolf or some other charismatic animal. This character will almost always be a girl who falls in love with Yuki and/or Kyo.
* Much of ''Anime/YuGiOh'' {{fanfic}} consists of inventing a new Millennium Item and a bearer to go with it. [[TheMovie This rarely ends well]].
** Parodies of this fandom cliché tend to have the ''Millenium Spork'' or something like that.
** This happens in the card game as well. Example: Millennium Shield.
** Not all Sues in ''Yu-Gi-Oh'' are Millenium holders; sometimes they're lovers/sisters/daughters of canon characters. A lot of the time someone's daughter/sister, someone else's lover, ''and'' have an item!
*** If Seto is the main character, expect the new character to be his new secretary or maid, or Mokuba's baby sitter.
** Joey has no special qualities yet often fights in important duels. Any duelist can join the fight pretty easily, with the only special thing about them is their actual skill.
** You could also just base your character around a certain archetype (I.E. Allies Of Justice) or strategy (I.E. Milling).
* ''Franchise/{{Pokemon}}'' fanfics involving aspiring trainers just starting out on their journeys... and written in a way that makes the canon human characters look like incompetent chumps. On the other hand, that isn't difficult to achieve, as writing characters with ''sense'' puts them miles above the canon cast, or at least [[IdiotHero Ash]].
** There's also an infinite number of newly introduced Team Rocket members. Those with a little more creativity just invent their own "Team Whatever" instead. Given that a new "Team Whatever" (or more than one, in some cases) is created in canon for every new region, this isn't surprising.
** This may also apply to the huge number of invented Pokémon people create. A few of them are creative enough, while most of them are not. A fan favourite would be made-up Eeveelutions. In one notable case, [[HilariousInHindsight fans came up with Leafeon, right down to the name, far before it was introduced in canon]].
*** Addressing both of the above, one site somehow managed to come up with not only the name Team Plasma, but nearly the same GOAL they had... in 2008. [[http://pokemonanrui.proboards.com/index.cgi Site here.]]
* ''SuzumiyaHaruhi:'' Either have a new member of the SOS Brigade be the ever-elusive Slider who hasn't shown up (assuming they don't follow the theory that ''Kyon'' is the Slider), or have Haruhi watch some movie and get interested in... vampires, wizards, robots, pirates, whatever.
* Given the ''{{Claymore}}'' system of ranks and the fact that we haven't seen all of them, it's easy to imagine a Claymore who hasn't been seen yet filling one of the vacant numbers. However, despite what some fanfics claim, there is no Claymore #48, since it's explained in-story that the Organization that makes Claymores specifically only assigns one to each of 47 regions of the setting making a #48 [[YouFailLogicForever a clerical error]] [[EpicFail of epic proportions]]. As one snarky reviewer of a fanfic of this sort said "And what region is she, then? The sky?"
* ''Manga/JoJosBizarreAdventure'' makes creating new Stand users simple: pick two musicians, bands, songs or albums, then name the user after one and name the Stand after the other. You don't even have to make the Stand's power correspond to the name in any way. There was originally a heavy bias for music from the '80s or earlier, but as time went on '90s references began trickling in, and part 8 even has Stands named [[Music/{{Rihanna}} California King Bed]] and [[Music/LadyGaga Born This Way]].
** When Stands were first introduced in ''Stardust Crusaders'', they were named after the major arcana of tarot (with or without an additional word--there's "Star Platinum", but there's also just The World), and later after Egyptian deities once the author had run out of tarot cards. One could potentially use the minor arcana, court cards, or alternate names of the major arcana, and the many leftover Egyptian deities (or ''any'' pantheon if you really felt like it).
* Though randomly adding a fifth member ruins the [[FourIsDeath numerical symbolism]] present in ''WeissKreuz'', Weiss have gone through so many new teammates they're practically the Rolling Stones of [[HitmanWithAHeart assassin teams]] -- and [[KarmaHoudini Schwarz]] aren't doing much better. The one canon team which ''has'' proved largely immune to the sudden influx of new female teammates is, ironically enough, the one team which was all-female to begin with.
** Notably, when Weiss does get two canonical new members in sequel series ''Weiss Kreuz: Gluhen,'' they both [[spoiler:die inglorious deaths]], making the scads of random new members who show up in fanfic [[DoomMagnet that much more nonsensical]].
* Any given series of ''Franchise/{{Digimon}}'' has a group of kids with {{Mons}} and Digivices, so generally it's a simple matter of picking a partner mon and a Digivice colour. Bonus points if the Digimon partner is entirely made up.
** For ''Anime/DigimonAdventure'', which already had an arc searching for a SixthRanger dubbed the Eighth Child, Sailor Earths often pop up under the title of the Ninth Child or higher.
** This is easiest in ''Anime/DigimonAdventure02'', which had a whole "World Tour" arc introducing kids with Digimon partners from outside Japan, and had the last episode state that, by the time of the DistantFinale, ''every single person on Earth'' has a Digimon partner.
*** Once upon a time there was at ''least'' one multi-author FanVerse solely dedicated to 02 and the exploration of this trope in conjunction with ElsewhereFic.
** Also rather easy in ''Anime/DigimonTamers'', in which they could have been another tamer whose wishes were granted, or their partner Digimon actively sought them out.
** ''Anime/DigimonFrontier'' also has four semi-canon (potential) Sailor Earth positions to be filled: the four remaining Legendary Warriors. You know, the PsychoRangers from the first half who never made a HeelFaceTurn? At least one fanfic has their spirits given to humans (in this case, all four of whom are somehow related to the heroes from ''Adventure/02''). The fact that [[FusionDance Advanced Hybrids]] do ''exist'' for Izumi, Tomoki, Junpei and Kouichi ([=JetSilphymon=], Daipenmon, [=RhinoKabuterimon=], and Reichmon respectively) but never got to be used, opens the door for DayInTheLimelight {{Interquel}} chapters to showcase them.
** ''Anime/DigimonSavers'' fics tends toward new members of DATS; it helps that it's mentioned in passing that other DATS units operate around the world, including the Austrian one Touma came from early in the series, so filling the gaps in in those is pretty easy.
** ''Anime/DigimonXrosWars'' fics generally involve the creation of a human general, a lead partner Digimon, and an accompanying Digimon army, though there's no indication that other human-led armies operated at any time during the war against the Bagra Empire. ''Anime/DigimonXrosWarsTheYoungHuntersLeapingThroughTime'' offers a more solid foundation - it's clearly mentioned that Digimon Hunting is something of a sport with many participants, so having another Hunter is pretty believable.
* ''Franchise/{{Zoids}}'', in the ''New Century'' and ''Fuzors'' series at least, involves an entire league of teams battling for fun, profit and prestige. How many fanfics have started with the main characters battling a new team? The same could be said of nearly any other competitive sports show out there; ''Anime/{{Beyblade}}'', ''Anime/CrushGearTurbo'', ''Anime/BattleBDaman''...
* New Card Captors with either their own Clow Cards or another set of Cards in ''Manga/CardcaptorSakura''. They tend to ignore the canon facts that 1. the Cards were a new form of magic invented by Clow; and 2. the Final Judgment couldn't take place until all the Cards were sealed.
* In ''Anime/OjamajoDoremi'', Sailor Earths often pop up as the green Ojamajo. Similar to the [[Franchise/KingdomHearts Organization XIII]] case, a green Ojamajo, Nozomi, actually showed up in the {{OVA}}s. The clue? [[spoiler:[[IllGirl She died from cancer]], and was the only character in the series to really die.]] Ever since then, a good chunk of Doremi fanfiction has revolved around [[spoiler:''reviving'' Nozomi.]]
** Which pretty much screws {{Canon}}, since it was stated that [[spoiler:you can't use magic to alter the fate of a person. If she died, then she can't be brought back to life]]. But most people tend to ignore it.
** Ojamajo fancharacters almost invariably show up as green, and named "Fasola," in order to establish some sort of ThemeNaming after Doremi. If not green, expect rainbow, or a mix of two or more colors, which will form an alternating pattern on their dress. Bonus points for black and/or red (even though, like [[spoiler:Nozomi]], there IS a red Ojamajo - [[spoiler:Poppu]]) or if they are somehow related to [[IdolSinger Onpu]].
* ''Manga/{{Chobits}}'' fandom is rife with extra Chobit-like persocoms, either as actual extra Chobits.
* The hosts of tailed beasts 3 and 5-7 in ''Manga/{{Naruto}}''. That a cover [[MilestoneCelebration celebrating the manga's 9th anniversary]] [[http://images2.wikia.nocookie.net/naruto/images/b/b5/Jinchuriki.jpg give designs for all of them]] despite [[spoiler:most of them being killed offscreen with little or nothing about them known]] just encourages this.
** [[spoiler: The 6-tails host, Utakata, gets his own filler arc in the anime.]]
** [[spoiler:For that matter, there apparently was no host for the Sanbi by the time we see it; Deidara and Tobi fight and capture the beast itself.]]
*** [[spoiler: Maybe by the time...it's been implied that the host of the three-tailed beast was able to control the tailed beast, and it's likely that he died and let him go. He ''was'' the Mizukage actually.]]
** Don't forget all the extra tailed beasts people come up with later, e.g. the ten-tailed wolf. Or the people who seal the yin half of the Kyuubi into another host.
*** [[spoiler: It was eventually revealed that a ten-tailed beast does exist, but it is actually the original tailed beast, the other nine being fragments of it split apart by the Sage of Six Paths]]
** The fandom also seems to be in the habit of inventing other members of the Seven Swordsmen of the Mist, of which only Kisame, Zabuza, and Chojuro have been mentioned. The more intelligent ones preserve the ThemeNaming and the odd swords. The less detail-oriented, and the filler writing staff, don't. Too bad all of them have showed up in the canon.
** For that matter, not only are the 5 major villages relatively little-known, but the canon map displays a dozens of tiny countries that could house new minor ninja villages (the filler writers certainly made good use of this).
** Not that there isn't plenty of Sailor Earth material in Konoha itself. Just have a character be from some second-tier clan with some "(usually a Japanese word)-gan" Kekkei Genkai. Or even make them a long-lost Uchiha or Uzumaki clan member.
* Until her identity was actually revealed, there were a reasonable number of fan-created red Cures for ''FreshPrettyCure'' based off of the fourth petal of the clover logo. Since said clover also had a green center, the idea of a green Cure or Cure-like ally was also popular.
** ''HeartcatchPrettyCure'' saw a few yellow and purple Cures (possibly due to the logo featuring yellow and purple in addition to pink and blue)...but only briefly, as Cure Sunshine and Cure Moonlight's appearances were leaked very early on. There is still Sailor Earth potential -- in this continuity, there were [[PrecursorHeroes numerous Cures who had their own adventures long before the main heroines did]], though they only appear in-series as anonymous statues.
*** This was even done ''in-universe''! When Potpourri was searching for the third Cure, he encounters Ban, who is trying to come up with a Sailor Earth of his own, Cure Fire, for his manga. When Potpourri suggests ''he'' be the third Cure, he starts imagining himself as such. Potpourri runs for the hills and Ban uses Cure Sunshine when she appears.
** ''SmilePrettyCure'' features a TransformationTrinket design with seven different-colored lights. Five of them correspond to the main characters. You can see where this is going.
*** In fact, there are [[FanWorks/PrettyCure fanfics]] revolving around ''entire teams'' of Sailor Earths.
** ''Anime/HappinessChargePrettyCure'' toys around with the trope, establishing other teams of Cures fighting the Phantom Empire around the world, thus allowing fans to come up with new Cures without affecting the core team.
* ''Manga/OnePiece'' features such cases as the third cousin once removed from Garp's side of the family, or brand new Straw Hats that have the "Whatever Whatever fruit."
** For years, the fan-made crewmember was almost always given the job of ship's musician. This was thanks to a RunningGag in the series where Luffy really wanted a musician for his crew, but could never find one. Fan-made musicians were typically very beautiful women (often mermaids) who played the harp or the violin with otherworldly skill (similar to Conis, who did not join the Straw Hats). The series put a stop to this when the canonical Strawhats finally got a musician, who is not a beautiful woman but a [[DemBones jovial dead guy.]] He ''does'' play the violin, though.
*** These characters still pop up in ''One Piece'' fics all the time, though; they're simply given a different job, often one that is made up for the fic (such as "helmsman", even though the crew has never expressed the need for one and usually just take turns at the helm). This likely stems from an early (and possibly outdated) statement by Luffy that he wanted ten crewmembers, and Jesus Burgess' position in the Blackbeard Pirates.
** Back before all the Warlords of the Sea were revealed, it was common for some OC villains to be this. This was back when Mihawk and Crocodile were the only ones revealed to be one and actually be made as characters, where Doflamingo and Kuma, while revealed, had little screen time. Other popular positions were Admirals and other high-ranking Marines. Since there are currently two vacancies among the Warlords and one Admiral with no information known other than his/her code name, there remains plenty of room for such characters.
** Particularly JustForFun/{{egregious}} when a Supernova OC will be introduced to "The Eleven Supernovas." Some authors will change the name to "The Twelve Supernovas," [[DroppedABridgeOnHim kill off an existing Supernova]], or [[TheyJustDidntCare ignore the name of the group completely]].
* ''Manga/RanmaOneHalf'' has no fewer than ''four'' very distinct plot elements to do this, all of which see regular use in fanfiction. The list is presented in no particular order and often they can combine into one mega plot device:
** A martial artist with a [[MartialArtsAndCrafts random martial art]]. Given the way the anime devolved into an [[MonsterOfTheWeek Opponent of the Week]] format, a new character with an appropriately thematic martial art style can literally wander into the Tendo Dojo to challenge Ranma. Even the manga allows for this, though not quite so easily.
** Ranma has [[LoveDodecahedron another fiancée]]. Yet another spurned fiancée wanders into the Tendo Dojo to enforce her claim on Ranma's hide, with a stolen dowry/contract backing up her claims. Thanks to the Noodle Race episode, which features a new fiancée showing up at the beginning of the episode and implying that Genma has done it more than once, there's plenty of ammo for a new character to be introduced. Again, even the manga provides for this with Ukyo (on Genma's side of things) and Picolett Chardin (for the extremely rare cases when a new ''fiancé'' for one of the Tendo girls shows up in fanfiction).
** Ryoga has a long-lost brother/sister/aunt/uncle/cousin. Ryoga explicitly states he rarely, if ever sees members of his family... and genuinely believed he had a sister near his age when Ranma tricked him with a disguise. It's not much of a stretch to assume he does, in fact, have family readers have never before seen.
** The Amazons/The Musk/The Phoenix Tribe. While the Amazons are the ones most often abused for the creation of original characters, each of the three provide for the character having some sort of mysterious background with the strength and martial prowess to be an appropriate match for Ranma.
** A fifth such plot element is the cursed training grounds of Jusenkyo. Pantyhose Taro's curse of Drowned Yeti-Riding-A-Bull-While-Carrying-An-Eel-And-A-Crane and Rouge's curse of Drowned Asura give them incredible fighting power, so an inventive author could use this all by itself.
* ''Manga/FullmetalAlchemist'''s Sailor Earths usually come in the form of homunculi with a randomly gothic-sounding name with the author trying to pretend it actually fits into the SevenDeadlySins ThemeNaming, or State Alchemists in their teens proficient in a ridiculous and completely useless field of thematic alchemy, completely disregarding the notion that State Alchemists are supposed to be [[PersonOfMassDestruction people of mass destruction]]. God only knows what use the Amestrian army has for alchemists with {{Code Name}}s like the "Starlight Alchemist" or "Angel Wings Alchemist." They also tend to forget that Ed is, canonically, by far the youngest State Alchemist in history, so bringing in one around his age is highly implausible. The distant third contingent is the Xingian royalty. Since it's stated that Ling has ''at least'' twenty siblings, his father has ''[[BigScrewedUpFamily fifty wives]]'', and we only know one of his half-sisters, Mei Chan, it's pretty easy for anyone to whip up their own prince or princess without much effort. This has never been as popular as the two first options, mainly because it doesn't apply to the better known first anime.
* Since the characters of ''Webcomic/AxisPowersHetalia'' are all {{Moe Anthropomorphism}}s of countries, it's very easy to create an OC by selecting any nation that hasn't shown up in canon; you can even opt to make a province like Canada's Quebec or The United States' states into a character. You're expected to do some research to make sure that your OC reasonably fits that nation/province's stereotypes and history, though, and inventing a country out of whole cloth just reeks of lazy writing and/or SelfInsertFic.
** Many people liked to put someone in for the missing North Korea, until a blurb on Himaruya's site was finally translated, stating many important details about him.
** A weird case happens with Latin American countries: Since the only Spanish-speaking countries that appears in the manga and the anime are Spain and Cuba, Latin-American fanfic writers loves to include Latin American [=OCs=] as part of the cast, even if many of those countries didn't had a steady contribution in WorldWarII.
** Just search Yakko's World Hetalia on Youtube to get an idea of just how many of these characters exist.
* ''ShugoChara'' fandom is rife with young girls who have over 3 charas, even if the series explicitly states that usually people have 1 or 2 at the most. Their response: 'Well, Amu can have three, why can't Sue?'
* ''Manga/SoulEater'' takes place in an ExtranormalInstitute and only focuses on three students at that school, leaving the rest of the students open to any fanfic writer's desires.
** Seven if you count the weapons (who do indeed have to attend classes and take exams.) Given that there are only six other students (three meisters and three weapons) who have even minor plot relevance, and barely more than that are so much as given ''names'', an author could easily add dozens of [=OCs=] without the slightest contradiction of canon.
* ''Manga/KatekyoHitmanReborn'' is a story with only the most prominent mafia families in that universe. Also, the Vongola might have quite a lot of enemy families. One can easily whip up their own family with some Italian-like name, and then fill it with many original characters (could be all girls). Then the story could be about Tsuna and co. meeting this family or getting attacked by this mystery family, resulting in allying [[LoadsAndLoadsOfCharacters with another original family]]. Also, many tend to disregard the fact that the point of having '''seven''' colors, '''seven''' flames, and '''seven''' core family/team members were to be a representation of a '''rainbow''' and its '''seven''' colors, so many authors write that Tsuna's family ends up expanding his family with more rings, and more colors (usually black or white, but sometimes an obscure color). Usually with more rings comes more characters to take on the role in the family. While some authors are a little thoughtful about the meaning of the positions they create for their characters, others only do it so the character is present and hooks up with one of the guys.
** Actually having more than seven rings and seven colors was sorta canon, as said in one of the games, but there was a specific reason why the topic of an eighth ring isn't touched upon.
** The Vindice seem to be the only known characters in canon that have access to the eight element, and it seems to be so powerful that [[spoiler: Daemon Spade thought that if he had it, he could beat the combined forces of Earth and Sky.]]
* ''KonjikiNoGashBell'' is a favorite with this trope because it allows for ''double'' Sailor Earth. Since most of the demon children on the run for Demon King were never introduced, it's no wonder fans write in their own Demons and Book Masters in periods were it was possible. Others goes as far as writing about ''another'' competition TwentyMinutesIntoTheFuture despite the main character's motivation being ''ending'' said competition.
** Though, at the end of the series, the main character [[spoiler:comes to realize that the competition is actually beneficial to both the human and demon worlds and alludes to the notion that the competition is actually necessary to choose the demon best-suited to rule and also teach the human and demon children valuable lessons that would otherwise stay unlearned.]] Thus, a subsequent competition isn't completely out of the question. In fact, who is to say that participants in past competitions had not come to the same realization?
* Though rare, ''Manga/YuYuHakusho'' fanfics may involve a future spirit detectives (since it is not stated whether or not Yusuke was succeeded by another teenager), another participant in the Dark Tournament or king's tournament, another student who wasn't taken by Dr. Ichigaki, a past student of Genkai, or someone from Mushyori city who became spiritually aware when the demon gate was opened (since Genkai stated that there were a lot more people who came to her after developing powers than just Kaito, Yana, and Kido).
* ''Manga/InuYasha'' Sailor Earths may be another human, demon, or hanyou who was cursed by Naraku or has another bone to pick with Naraku for some reason. Naraku ''does'' have a ZeroPercentApprovalRating, so it is only natural everyone has a bone to pick with him.
** Or you can make a Sailor Earth as one of Naraku's new incarnations or spawn, since he seems to pop a new one out every fifty chapters or so. He's had a dozen or so with various ElementalPowers, so creating a new incarnation doesn't take much imagination.
** The real Sailor Earth in this series is when fanfic authors give Inuyasha another sibling (oftentimes a sister). Sometimes with their own super sword from their father (that is often even more powerful than the swords he left his canonical sons). The problem with this is there ''WAS A THIRD SWORD'' (movie three featured [[FillerVillain Sou'unga, the Sword of Calamity]]). And it was indeed more powerful than either of the other two (if they tried to take Sou'unga alone).
** Inuyasha, the hanyou whose father had many daughters when he was already dead. Then again, some people in this anime seems to have a problem with staying dead.
** [[VideoGame Bandai Entertainment]] did this to their ''Manga/InuYasha'' RPG adaptions. ''The Secret of the Cursed Mask'' for PS2 has either a boy or a girl and ''Secret of the Divine Jewel'' for NDS has an American transferred student Janis, all that are pretty much Kagome's {{Expy}} upon their introductions. While they have their own plots, the whole point is only to have their original characters go on a quest along with the FiveManBand.
* ''OuranHighSchoolHostClub'' fanfics seem fond of introducing a new member of the Host Club out of nowhere.
** Another popular tactic is to make a ''Hostess'' club and create five or six new characters at once.
* ''MermaidMelodyPichiPichiPitch''...oh, good luck finding a fic that doesn't introduce a hitherto unknown "red" mermaid (despite the fact there are no oceans left for a mermaid to represent... but then writers can get creative with things like "the Bering Sea" mermaid). If it's not red, colors can start from white and can get extremely ridiculous, to the point of having "metallic colored" mermaids and mermaids with the color of "tangerine" and "mint". Other fics choose to take the fact that [[spoiler:Lucia is the next Aqua Regina and thus pick another girl to be the Pink Mermaid. If the writer has not caught up with the manga or has only watched the anime, the "new mermaid" can be the next Aqua Regina.]]
* ''Manga/DeathNote'' has Wammy's House, with 26 letters (or the combined total of all alphabet letters) of Sailor Earth goodness, for your crazy detective needs, usually a crossover of CopyCatSue of L or other canon Wammy attendants.
** And some people who believe the Latin alphabet isn't good enough have started resorting to Greek letters and other foreign languages...
* The number of unused ''Three Kingdoms'' or even ''DynastyWarriors'' characters in BBSenshiSangokuden, coupled with the immense amount of leftover Gundam mecha provide prime fodder. Xiao Qiao Methuss, Cao Zhi Airmaster, Cao Ren Leopard...
* For ''KamichamaKarin'', all you need is another Greek god. Some people don't even stop there and start recruiting gods from other mythologies as well. Oddly, there seems to be an even split between making new characters and just giving the existing ones new powers.
* ''TenchiMuyo'' fics tend to fall into this trope. Either a new girl joins Tenchi's "Harem" who naturally has superpowers of her own (to varying degrees of awesomeness) and usually develops feelings for Tenchi too, coming into the usual conflicts with Ryoko or Ayeka. OR add a male character, with super powers of some sort (natch), usually to be a boyfriend to one of the various girls at the Masaki household, since Tenchi has so many of them lying around.
* ''MagicalGirlLyricalNanoha'', from ''[=StrikerS=]'' on with its MildlyMilitary setting, allows for the existence of other TSAB teams and units that can act alongside the canon characters.
* It's very easy to make a magical girl for ''Anime/PuellaMagiMadokaMagica'', what with the ''billions'' of girls on earth to be contracted in past, present ''and'' future, and the revelation that Kyubey's kind visit other planets as well only made it easier. The only ''real'' requirements are [[spoiler: they have to have misery in their lives in some way, their soul is now outside of their body, [[BreakTheCutie and they will either break]] [[KillTheCutie or die,]] depending on how cruel you are.]]
** One can even make another Incubator if they wished. Since ''Manga/PuellaMagiKazumiMagica'' revealed [[ThemeNaming Juubey]], people are running with the idea of them being a numbered series. [[spoiler: As it turned out, [[RogueDrone Juubey was a special case]], and his name isn't (entirely) a number pun.]] The theory has been {{Jossed}} to some degree, since WordOfGod and several spinoffs suggest that the species is an [[TheStoic emotionless]] and uniform HiveMind. However, Kyubey admits that there are members of his species who suffer from a "[[GrewBeyondTheirProgramming mental disease]]," which has prompted the creation of many a DefectorFromDecadence... or the occasional creature that would be evil [[EvenEvilHasStandards even by their standards]].
** If your story is set previously to the end of the series, it is also fairly easy to create your own [[EldritchAbomination Witch]]. There is pretty much an infinity of them all across the ages, with an infinity of gimmicks, new ones appearing every day. There's even a template all laid out for you by the official descriptions: a name, a [[MindScrew mindscrewy]] design, a nature and a short description for the witch herself. Another name, design, duty and short description for her minion. Given that "birdcage witch" and "class representative witch" are valid Witch gimmicks (both appear in the anime), then you can see Magical Girls can ''never'' run out of enemies to fight.
** As shown in ''Anime/PuellaMagiMadokaMagicaTheMovieRebellion'' [[spoiler: witches can still appear after the end of the anime, but only under special circumstances. Also, they can now be [[GuardianEntity Guardian Entities]], or the result of VoluntaryShapeshifting.]]
* Thanks to ''Anime/MobileSuitGundam'''s rich history, especially in the Universal Century, it's not impossible for some hotshot rookie who is a Newtype/Cyber Newtype/Gundam Fighter/Coordinator/Innovator/what-have-you pilot some super awesome Gundam to fight the evil forces of Zeon/The Titans/Neo-Zeon/Crossbone Vanguard/Zanscare Empire/OZ/ZAFT/A-Laws/what-have-you. It doesn't help that, in the One Year War-era, we've seen tons of fronts of the Federation/Zeon war and that, in the ''Anime/MobileSuitGundamSEED'' universe, Gundam isn't actually the name of the awesome SuperPrototype - it's the name of the OS. ''Everything'' there is a Gundam!
** A good rival for this kind of character would be a mysterious man with a CoolMask who pilots a red Mobile Suit with three times more advanced specs than the standard model. Why not? [[CharClone It's common in canon!]]
** And it's really easy to come up with new Mobile Suits. Simply take an existing model (Zaku, Leo, GINN), change its design a little, and you have an instant variation. It's flat out encouraged by the [[AllThereInTheManual Mobile Suit Variations supplemental material.]]
** Doesn't happen as often as you'd think with the fan-favorite ''Anime/GundamWing'', since [[MostFanficWritersAreGirls most writers]] focus on [[{{Bishonen}} other]] [[HoYay subjects]] ''besides'' the war with OZ. Interestingly though, ''VideoGame/ShinSuperRobotWars'' pulled a variation on this by making the OriginalGeneration mecha R-Gun the Wing Team's SixthRanger, even having it be designed by Howard, a canon character who may have had the know-how to make a Gundam but not the inclination.
* The premise of ''Franchise/BlackRockShooter'' makes it very easy to come up with one. ''Every person in the world'', or at least every girl, is implied to have an Other Self in Otherworld, and so all fans need to do is fill in the blanks. A new person, usually a girl, easily gets shoehorned into Mato's school as a new student (or employee) with some sort of {{Angst}} and the corresponding Otherself, or the fan just dreams up their own Other Self. In addition, the existence of [[PaletteSwap White]] [[IdenticalStranger Rock]] [[EvilTwin Shooter]] practically begs for the creation of various [[CopyCatSue Copy Cat Sues]] and [[{{Expy}} Expies]] of the eponymous character.
* In ''Manga/FairyTail'', these usually manifest as previously unknown Dragon Slayers, the most popular being of the [[MakingASplash Water]] element. [[AnIcePerson Ice]] and [[DishingOutDirt Earth]] (the element, not the planet) are also somewhat prevalent, along with a couple other, weirder ones, like Crystal or Light.
** Some people like to create new Celestial Spirits for Lucy (or, rarely, for a fancharacter) to use. As there are literally dozens of unused constellations to choose from, this leaves open a lot of potential. However, instead of being Silver Keys like all non-Zodiac constellations are ''supposed'' to be, these sometimes get hit with super-powerful White Keys or Dark Keys. Common constellations for these super keys include Pegasus, Canis Major, and Draco.
*** Ophiuchus ''used'' to get hit with this sometimes as a lost Zodiac member, but then he made a canon appearance as an actual 13th "forbidden" Golden Zodiac key belonging to Yukino. Appropriately for his darker nature, his key is black (gold with a black snake entwining around it in the anime).
* Because ''Manga/DGrayMan'' only focuses on the activities of Allan's small group of Exorcists and a few Generals despite the Black Order having multiple branches across the world, it's not unlikely for people to create more Exorcists from those branches. Generals are included into the mix. Also, because of the lack of a recruitment age for Exorcists, many of them and some Generals tend to be implausibly young for the job.
** It doesn't take much imagination to come up with an Exorcist either. In general they need a weapon (usually a cool one - {{Sinister Scythe}}s are popular) and an experience with Akuma before being recruited.
** When a new type of Innocence was introduced, many characters swiftly took on that type despite not having a lot of information on it at first, only based on the knowledge that the base two types of Innocence can transform.
** Any new Noah is guaranteed to have their own ability/ies and usually highly sadistic and attractive since it's not stated how many Noah there are total. Anyone normal-looking can turn out to be a Noah.
** Thanks to TheReveal about Allan and his connection to the Noah, there are inexplicably quite a few half-Noah Exorcists hanging around even if it's stated that Noah hate Exorcists.
* ''Manga/AttackOnTitan'' focuses on the 104th Trainee Corps, so there are plenty of characters hailing from past Trainee Corps who have survived to the present time of the story. Information released also indicated that there are North, East and West batches of trainees apart from the South batch (which is the focus of the story), and since the top 10 students are from each batch rather than from the entire 104th it is possible to make characters join the elite Military Police and claim they're not from the South 104th, to make up for the 30 trainees who aren't seen.
** The Stationary Guard/Garrison's massive numbers compared to the other military branches makes space for a lot of characters in various brigades or divisions.
** Can't forget the Titan Shifters. They usually have unique traits like the Shifters in the story, and either are for humanity or against humanity.
[[/folder]]

[[folder:Comics]]
* This happened to an explosive degree in GreenLantern's Sinestro Corps War, with legions of ring wielders for every color either coming into existence or being hinted at.
** Sodam Yat. The longstanding fanboy desire to see what Superman would be like with a Green Lantern ring was satisfied after a fashion by giving a ring to a Daxamite. At first he was simply an exceptional ring wielder, then the Oans revealed to him that yellow sunlight would give him Superman-like powers and as his body was charging with solar energy the first time, they gave him the Ion entity which took his Green Lantern powers to the next level.
** There was actually a [[Franchise/StarTrek Vulcan Green Lantern]] once, who appeared in a page of an issue of the series in the 1970s. While unnamed, the character even makes the Vulcan Salute! He was just sight gag/ShoutOut at first, until the current ContinuityPorn-filled run brought him back, named him Saarek, and gave him a gimmick: he's apparently a medium/necromancer.
** There's the ''Pierson's Puppeteer'' GL seen in the Larry Niven-authored graphic novel ''Ganthet's Tale''; though most likely simply a ShoutOut to the author on the part of artist John Byrne, the thought of a fearless Puppeteer (because this was before the recent retcon to the GLC's primary qualification) makes the mind boggle. And Byrne drew it with a neat mane, too, so either it was so insane that it came out the other side into sanity, or a [[GreenLanternRing Power Ring]] can be used as a hair care tool.
** There's fanart of just about anybody and their brother (anime/manga/game/TV/movie/book characters included, plus non-DC comics) with the color of ring most suited to their personalities.
** Also, in spite of the fact that this theory has been allegedly {{Jossed}} by Geoff Johns, the idea of the colors uniting to form the white light of creation to combat the Black Lanterns has led to the creation White Lanterns in many fandoms. The lead up to ''Brightest Day'' only fueled it further.
** Common fandom jokes: Brown Lanterns, aka the Apathy Corps. Also Infared and Ultraviolet Lanterns.
* This was extremely easy in ''Comicbook/{{X-Men}}'' fan fics. Everything from new members, new students at the school, even entire teams could be dreamed up easily, since the only criteria is that one was born with his powers (and even that isn't set in stone).
** Grant Morrison revealed in ''[[Comicbook/{{X-Men}} New X-Men]]'' that, in the Weapon X program Wolverine belongs to, X is actually the roman numeral 10. He then introduced Weapons [[CaptainAmerica I]] through XV.
* The title character of ''10th Muse'' is, you guessed it, the tenth daughter of Zeus and Mnemosyne - the muse of justice (because, you know, comic book). Her archvillain? Mnemosyne's only son.
[[/folder]]

[[folder:Film]]
* The setting of ''Film/TheMatrix'' lends itself extremely well to original characters: just have someone new get unplugged from the Matrix. In fact, you can make a whole ship full of [=OCs=] if you want (preferably with a classical name, in the tradition of the ''Nebuchadnezzar'' and the ''Osiris''). [[SturgeonsLaw In most cases]], the fact that the vast majority of redpills are unplugged well before adulthood will be addressed in one of two ways: if the fanfic writer is an adult him/herself it'll be overlooked, and if they're a teenager or younger it'll be used to justify making the character their own age.
* ''Film/TheLeagueOfExtraordinaryGentlemen'' fandom is rife with fics picking up after the end of the movie (less so the comic) which introduce a new member to the League. Said member is 99% likely to be young, female, beautiful, and possessing a power not already present in the cadre. Lycanthropy is popular, but so are various PsychicPowers. Often this character will have some connection to one of the canon characters, like a previously-unknown daughter or sister; one example that comes to mind is a fic which gave Mina Harker a sister who was a werewolf; not only did the sister also have the last name of Harker (Mina's ''married'' name), but the novel ''{{Dracula}}'' explicitly identified Mina as an orphan with no living relatives. A slightly more creative writer might instead go with the offspring of a literary character who didn't appear in canon.
* ''RealSteel'' introduces a world where boxing is now done between robots. Each robot has a different theme, and many of them are implied to be homemade. All a fanfic writer would need to do is create a robot, and give it a BackStory. The film and additional material related to it give many facts for {{Worldbuilding}} as well; for example, robot boxing originated in Japan.
* ''{{Newsies}}'' is a gold mine for this kind of thing; pretty much the only thing all Newsies have in common are evocative, character-defining nicknames, and a hard-luck past. There's also the historical existence of less common girl Newsies (although none appear in the film), but good luck finding a Girl Newsie story where she isn't the only girl living among all the boys.
* Every other ''Film/SkyHigh'' fic seems to involve a new, oh-so-speshul student at the school with an [[OverlyLongName improbable name]] and various ComboPlatterPowers who quickly becomes the center of everything and makes out with [[{{Adorkable}} Will]], [[AllGirlsWantBadBoys Warren]], [[IdiotHero Zach]] or even ''[[DracoInLeatherPants Lash]]'' if [[MarySue female]] and [[UnluckyChildhoodFriend Layla]] or [[DatingCatwoman Gwen]] if [[MartyStu male]] (we're not sure if we should pity or envy [[DeadpanSnarker Magenta]] and [[BlackAndNerdy Ethan]] that they're typically spared all this nonsense). The prevalence of such characters is without a doubt due to the sheer ease with which they can be created; there are almost certainly students and even teachers we didn't see in the film, plus the various unnamed characters we ''did'' see, all with unknown powers, and as noted above under 'General' the school setting makes "transfer student" a logical way to introduce a new character, as well.
* There are quite a few ''{{Ghostbusters}}'' franchises within the United States and worldwide, many of whom do charity events, fundraisers, and the like.
* Though not as common as they once were, a lot of ''Film/StandByMe'' fics tend to retell the plot of the movie with a girl being the group who accompany the boys on their trip to find Ray Brower. Three things you expect from these fics: A) the girl will be the narrator instead of Gordie. B) the girl will always be a "Tomboy" or at the very least be the "Least girlest girl ever". And C) be head over heels in love with Chris Chambers. Either confessing her feelings for him during the journey or, if the author continues on from the journey, confess during their teenage years. There are also fics that add a girl to the Cobras.
* ''Film/NowYouSeeMe'' fics will add a fifth Horseman to the group. Almost all are female teens and young adults, so as to be a love interest for Jack Wilder.
[[/folder]]

[[folder:Literature]]
* New ''Literature/HarryPotter'' classmates, especially ones that they would never let be enrolled at Hogwarts in the books or movies. This could include such canonical characters as Blaise Zabini, whose existences were ''known'' but who had never appeared "on screen".
** Students (or former students/graduates) of Beauxbatons or Durmstrang may also show up.
** And what about exchange students from [[{{Eagleland}} The Salem Witch Institute]]? Obviously common whenever an American fan wants to do a self-insert fic, with a variant being to use some of the canon characters as exchange students ''to'' an American wizarding school.
** There is also the common variant of Japanese exchange/transfer students, thanks to the frequent crossover between the anime and Harry Potter fandoms. (Especially common on [[GaiaOnline Gaia]] roleplaying guilds.) This was helped when Pottermore [[http://harrypotter.wikia.com/wiki/Mahoutokoro named a Japanese school]] Some RP groups address both problems by explicitly banning Hogwarts student characters who were not born in the British Isles.
** New professors, too; Defense Against the Dark Arts professors are of course especially common given the position's turnover rate. Implausibly young ones are worryingly common.
* ''PercyJacksonAndTheOlympians'' is constantly prone to a new demigod, which is made extremely easy by the ending of the fifth book [[spoiler:stating that more and more demigods will be claimed and are coming across the border to Camp]]. And the sequel reveals [[spoiler: that there's also a camp for the children of [[LiteralSplitPersonality the Roman gods]]]]. And ''then'' the sister series gave us not only characters [[spoiler: descended from Egyptian gods]] and an AncientConspiracy, but pretty much confirmed they all exist in the same 'verse. Even further, WordOfGod has stated that the next series will feature the Norse Gods
* Fan fiction for ''Literature/TheLordOfTheRings'':
** Stories with a "Tenth Walker" in the Fellowship of the Ring are suprisingly common. There are only Nine Walkers in {{canon}}, so these stories are really {{Alternate Universe Fic}}s.\\
\\
The name "Tenth Walker" references ''[=LoTR=]'' Book II Chapter 3, when Elrond declares, "The Company of the Ring shall be [[ArcNumber Nine]]; and the Nine Walkers shall be set against the Nine Riders that are evil." After setting the number, Elrond chooses Nine and only Nine to become companions.
*** Some authors let the Nine leave Rivendell, and the Tenth Walker joins later.
*** Most stories with a Tenth Walker follow [[Film/TheLordOfTheRings the movies]], not the books. In the movies, members volunteer themselves, then Elrond announces, "Nine companions. So be it. You shall be the Fellowship of the Ring." It is easy to insert another volunteer and change Elrond's line to say, "Ten companions."
*** Some stories have Eleventh Walkers, Twelfth Walkers and so on.
*** The official board game indulges in a bit of this by having Fatty Bolger accompany the rest of the hobbits to Mordor rather than staying in the Shire. It ignores the Nine = Nine idea because it doesn't use the Fellowship, only the hobbits.
*** A few writers get around the "nine walkers for nine ringwraiths" issue by adding a tenth ringwraith to correspond to the tenth walker.
** ''FanFic/TimeWillTell'' is unusual, because Jorryn joins the hobbits from Shire to Rivendell, but never becomes a Tenth Walker.
** A few authors invent a 21st [[RingOfPower Great Ring]], though canon has only twenty. Gandalf briefly mentioned some "lesser rings" in ''[=LoTR=]'' Book I Chapter 2.
** A few authors invent a sixth wizard. Canon has exactly five Istari.
* In ''Franchise/JamesBond'' fanfics, there will often be a character whose codename is either 00x or a letter besides M and Q. This is not helped since the movies have, at various times, either shown or mentioned 3 different 006s, 3 different 009s, 2 different 002s, a 003, a 008, and even a 0011. Most of the other 00 agents that have more than a passing mention in the movies tend to wind up dead shortly thereafter. It's very clear that not only do numbers get recycled when their former owners die, but that any given number works as long as it's preceded by 00 -- making 0013, 0069, 0099, or even 008675309 all valid code-names.
** Makes sense; 00 is simply an agent status, showing they have license to kill.
** Combined with the EpilepticTree that James Bond is merely a code name, there exist plenty of fanfics starring a brand new Bond after the previous one was killed/retired. At least it's better than ones about Bond being a WMG/TimeLord.
** Mildly lampshaded in the film version of ''Casino Royale'' - James to M: "Well, I understand double 0s have a very short life expectancy..."
* The ''[[Literature/WarriorCats Warriors]]'' fanbase is notorious for this. Most Warriors fanfics have no involvement with the canon characters (either the writer will create new Clans or write about the book Clans in a different time period than canon). In fact, it's so incredibly common that it's often seen as Mary Sue-ish for a fancharacter to exist amongst the canon characters.
* Quite a few ''Literature/{{Animorphs}}'' fanfics have somebody new join the team. This plays out interestingly, because the Animorphs already had a SixthRanger, but he [[SixthRangerTraitor sold them out to Visser Three]] to get his parents back. So, naturally, there is some skepticism in the group if they want to take in another new member, TouchedByVorlons or otherwise. But it gets resolved within a chapter, after the OriginalCharacter promises not to kill them in their sleep, and Marco mentions he needs a pairing buddy.
** Another obvious mechanism: Vissers. Vissers Three and One are recurring villains, and with 47 Vissers, only a few of whom we've met, it's easy to bring in a new one.
*** This was actually one in-canon, Visser Four, whose only appearance was after being disgraced. He apparently found [[spoiler: the Time Matrix]] and used it to try and preemptively soften up the human race, but [[spoiler: Cassie erased his host from history by making sure his host's parents didn't have their MeetCute.]]
** ''Alternamorphs'', the ChooseYourOwnAdventure spinoff media, actually embrace this trope. In the second one, the reader even plays as [[ForegoneConclusion the aforementioned Sixth Ranger]].
** There were also the Auxiliary Animorphs who were mostly people who were not suitable controllers (due to being disabled in some way), and a fanfic can easily put the new character in the shoes of one of them, sometimes with varying disabilities. (A good example would be somebody who is autistic and wouldn't be suitable because different behaviours would alert non-controllers that something is up.)
*** There can also be another faction of Auxiliary Animorphs who were deemed unsuitable controllers for other reasons - such as they are children and are too young to be of any use as of yet, they're too old, or they do not have the proper social status to become a good controller.
* ''Literature/TheClique'' has a common theme in their fanfiction: A new clique [[CopyCatSue that resembles the original one]] comes in and competes with the Pretty Committee. The new clique is either lead by a [[CopyCatSue Massie-esque bitch]] that happens to beat Massie when it comes to hurling insults, or a [[PuritySue total sweetheart]].
* 99% of fanfiction for Mary Hoffman's ''Literature/{{Stravaganza}}'' series involves the introduction of a new Stravagante. Which, in fairness, is how every book in the series starts.
* The ''Franchise/StarWarsExpandedUniverse'' uses this quite often, usually in a good way.
** Obviously, at the end of ''Return of the Jedi'', Han/Leia is standard, but what about Luke? Enter Mara Jade.
** Who helped Leia get the Death Star plans? A former stormtrooper turned mercenary turned Jedi Knight named [[VideoGame/DarkForcesSaga Kyle Katarn]].
** Luke needs Jedi students, so... Kevin J. Anderson gave him a dozen.
*** In the FixFic ''I, Jedi'', in addition to that dozen, Mara, and Kyle, we have Corran Horn.
** The surviving Y-wing pilot from ''A New Hope'' is canonically you in the ''X-wing'' games.
** So we have Jacen, Jaina, and Anakin. They need friends to join in on their adventures, plus show romantic subtext. Hence Tenel Ka, Zekk, and Tahiri, respectively. There's also Lowbacca.
* ''TheRailwaySeries'' has [[AllThereInTheManual ''The Island of Sodor'' and ''Sodor: Reading Between The Lines'']] which suggest that there are eighty locomotives on the Fat Controller's railway alone, as well as a number of engines formerly working on Sodor and several branch lines, minor railways and industries that could be rail-served. Fanfic characters are therefore usually just a case of finding a gap in the Sodor stockbooks and dropping an engine (often [[AuthorAppeal the author's favourite class of locomotive]] ) in. In many cases, as real locomotives have been turned into characters in the series proper, creating a character is often as simple as putting a face on a real engine and inventing a reason for them to come to Sodor.
* Most ''{{Holes}}'' fanfics have someone new coming to Camp Green Lake - and it's almost always a girl, despite the fact that it's an all-boys camp. This is rarely even {{Handwave}}d.
* Lost Targaryens in ''ASongOfIceAndFire'' fanfic who just ''happen'' to stumble on dragon eggs and start conquering stuff.
** There are a lot of noble houses in Westeros, but only a few of them have names: the rest are only mentioned by their heraldry. This allows for would-be Sailor Earth makers to create their own house by making up a coat of arms or taking one of the many heraldic designs described in the book. The ''A Song of Ice and Fire'' tabletop RPG by Green Ronin includes this as an option in its character-building process.
* In ''Literature/TheHungerGames'', there are 73 past Games, meaning 73 opportunities for fans to invent their own victors (who are, [[SturgeonsLaw mostly]], {{Mary Sue}}s) provided they're not accounted for (after all, [[spoiler: the 75th Hunger Games had a special gimmick that past victors are Tributes]]). Not only that, but it also provides opportunities for 23 other Tributes, leading to a grand total of 1776 total Tributes that may or may not have been accounted for. There's also the Quarter Quells, special Hunger Games with different gimmicks. It's mentioned that there's more than three and they could stretch out to last hundreds upon hundreds of Hunger Games. And of course, if you wish to invoke the WhatIf scenarios, [[spoiler:[[LaserGuidedKarma A Capitol Tribute-based Hunger Games]] and [[BadFuture Hunger Games stretching from the 76th onwards]] are possible, and thus the Victors, Tributes, and Quells grow]].
* The ''DragonLance'' series has an interesting inversion in the official ''Tales'' trilogy; a historian claims to have discovered evidence that there was a gnome member of the original 'Heroes Of The Lance', who was written out of the Chronicles and his existence completely hushed up by the rest of the heroes.
* With ''DragonridersOfPern'' fics and RP fora, this tends to manifest itself mainly in four ways - all of which have ''some'' basis in canon:
** A dragon outside the five standard colors (female Greens and [=Gold/Queens=], and male Blues, Browns and Bronzes); one that isn't a sport or a runt like Ruth (canonical White dragon). Often written to have special abilities (the ability to talk physically as well as mentally being a popular one).
** Female Bronze/Brown riders and male Queen riders.
** Riders with Journeyman Craft ranks (Usually Harpers)
** Children of Lord Holders (Pern equivalents to princes and princesses) becoming riders.
** [=McCaffrey=] kind of brought this on herself, as the canonical Jaxom is both a rider and Lord Holder (not just the ''child'' of a Lord Holder, but an actual Lord Holder, though for most of his book he's underage and is only ''nominally'' the Lord Holder), who ''also'' has a non-standard-colored dragon (the aforementioned Ruth). She should have just called him [[MarySue Marty]] and made him a Harper to boot.
* The majority of ''MaximumRide'' fanfics and [=RPs=] features a new mutant or group of mutants that has broken out of a lab. The former always joins up with Max's [[spoiler:or Fang]]'s flock and the later usually becomes their own.
* HPLovecraft's CthulhuMythos is essentially a huge bunch of professional fanfics of the CosmicHorrorStory's TropeCodifier (and was that way even during Lovecraft's life as he and his author friends freely cribbed from each other), so many writers have added more and more [[TomeOfEldritchLore forbidden books]][[http://en.wikipedia.org/wiki/Cthulhu_Mythos_arcane_literature]], [[StarfishAliens weird species]][[http://en.wikipedia.org/wiki/Category:Cthulhu_Mythos_species]] and [[EldritchAbomination god-things]][[http://en.wikipedia.org/wiki/Cthulhu_Mythos_deities]] (as well as Masks of [[http://en.wikipedia.org/wiki/Nyarlathotep Nyarlathotep]]) to the mix. Arguably a positive example, as many of these these have become quite popular among fans.
[[/folder]]

[[folder:Live Action TV]]
* Any series with a MonsterOfTheWeek formula, like ''{{Smallville}}'', makes it easy to introduce a new superpowered character.
* This is easier in ''Franchise/PowerRangers'' than you might think. Considering nearly every team leaves at least one common ranger colour out and the canon [[TheSixthRanger Sixth Rangers]] are allowed to join up late too, all it takes is to pick a season, pick a colour they didn't use, throw a little ''DeusExMachina'' in here and there and voila! The White Ninja Storm Ranger! The Green Dino Thunder Ranger! The Black Mystic Force Ranger! And that's without even getting into non-canon ranger colours.
** Parodied in ''[[Series/PowerRangersSPD S.P.D]]'' in which one of the minor characters lied to his parents, claiming he was not just a ranger, not just the ''leader'' of the Power Rangers, but the first ever ''Orange'' Ranger. Ironically, ''Franchise/SuperSentai'' did once have an Orange Ranger: Battle Cossack from ''Series/BattleFeverJ.''
** With the government/military-based teams, it becomes a very simple thing to have a random joe in the organization get promoted and saddled with a blank power template. This is especially the case for ''S.P.D.'', which canonically had several squads of Rangers already.
** There are entire ''teams'' created to fill a Power-Rangers-Equivalent of Sentai teams preceding ''Series/KyoryuSentaiZyuranger''. Or the five normal [[Series/GoseiSentaiDairanger Dairangers]] who never got their suits used. Some even go ahead and make future Ranger teams based on future Sentai teams; currently, ''[[Series/KaizokuSentaiGokaiger Gokaiger]]'' is one popular choice, though it's no longer future as of ''Series/PowerRangersMegaforce''.
** Thanks to the number of additional mecha that get piloted remotely, it's easy enough to design new Rangers after them. Canon already has the Titanium Ranger (whose colors don't even match his Max Solarzord, but still counts) and the ''[[Series/PowerRangersJungleFury Jungle Fury]]'' Spirit Rangers. In toy form, we have the hideous repaints of the [[Series/PowerRangersOperationOverdrive Operation Overdrive]] Rangers that come with the bikes, and three original Rangers for the Paleomax Megazord of ''Series/PowerRangersRPM''. Those are just the tip of the iceberg when you consider that ''Series/PowerRangersWildForce'' by itself has up to 94 unassigned Wild Zords, the majority of which were never defined in the show...
** There's also the Rangers or Ranger-like heroes that were in the {{Great Offscreen War}}s and {{Cryptic Background Reference}}s - previous ''Wild Force, Mystic Force'', and ''Samurai'' teams existed and ''so'' little is known of them. Lotsa fanfic fodder there.
** A canon example exists for ''Series/NinpuuSentaiHurricanger'' in the form of [=TentoRaiger=], introduced in the second season of ''Series/HikoninSentaiAkibaranger''. However, she was a villain- so naturally, the door is left open for fans to imagine what a version of her on the side of good would be like.
* There are several teams in ''Series/StargateSG1'' that have been mentioned but never seen, leaving a lot of wiggle-room for fans. This one especially is ''really'' easy, as not only is Stargate Command just a US Government agency instead of some weird group of Destined Ones, "SG-1" itself is just a serial designation. Want a full roster of [=OC=]s? No problem, welcome to SG-7. Making it even easier is the fact that there are at least 9 SG teams in canon from the very first episode, up to at least 25 by the 10th season, with the audience getting to see what SG-1 is doing 99% of the time, with the occasional appearance to SG-2, [[SemperFi SG-3]] or SG-4 members. That's at least 100 potential characters. Add to that the fact that the teams are at least somewhat specialized (to say nothing of the Russian team, with a new one most likely being formed after SG-4 was wiped out), and you've got even more to play with. And that's not even counting the people who are almost certainly going to add SG-0 as a secret black ops unit that's better than SG-1 but who nobody knows about.
** With the upcoming ''Stargate'' [=MMO=], it seems likely that players will get to take their SG-Whatevers into the virtual plane. Watch as clans of avatars take on even the toughest of Goa'uld! Of course, video games are generally all [[TheChosenOne about]] [[TheUnchosenOne that]].
** The Goa'uld themselves. Even with the necessity of excluding the Norse pantheon, there's a vast number of mythological deities who were never used in canon. That's a lot to pick from if a fanfic writer wants an OC villain for their OC characters to confront. And with regard to the Norse pantheon, only a handful of the Asgard actually made appearances in canon.
* The same thing happens with ''Series/{{Torchwood}}'', for which the main characters for series 1-3 worked for "Torchwood 3" -- though canon gives explicit designations for 1, and 2, 4 has vanished and is easily brought back for fanfic purposes, and it's not entirely ridiculous to imagine there's Torchwood 5, 6, e, -90423, or what have you. [[spoiler:By ''Children of Earth'', however, it seems that all Torchwoods had been shut down, leaving only a remnant successor with no permanent base [[Series/TorchwoodMiracleDay two years later]]]].
** It used to be that you could at least insist Torchwood was solely based in Britain. Following the introduction of Torchwood India in the radio drama "Golden Age", it's quite reasonable to assume there are branches all over the former British Empire, as Torchwood was founded by Queen Victoria.
* As noted above, SpaceOpera shows can get this. Especially common are ''Franchise/StarTrek'' fanfics about Starfleet, since we don't even know how many ships there are. At an absolute minimum there must be hundreds. There are many ships that the main heroes cross paths with for one episode, and it's easy to crew them with [=OCs=].
** It's also possible to do it with ships, as they have themes. Need a new [=DS9=] runabout? Think of a river! Need a new ship the same class as the local version of the ''Enterprise?'' Think of a modern battleship!
** This is also possible with military and crime stories in a contemporary setting like ''Series/{{JAG}}'', ''Series/{{NCIS}}'' & ''Series/NCISLosAngeles''.
** This is done in the ''StarTrekNovelVerse'', in which the ''Titan'', Riker's command as of the end of ''StarTrekNemesis'', is a ''Luna''-class starship, and each starship in that class is named after a moon...thus giving endless FanFic opportunities there. Nor does it necessarily have to be a moon from our solar system; for example, the names of two Bajoran moons are known. Likewise the ''Literature/StarTrekDestiny'' series establishes that there are at least seven ''Vesta''-class ships, four of which are named after four of the seven hills of Rome (meaning Palatine, Viminal, and Caelian are still open).
* ''Franchise/KamenRider'', especially in the Heisei era, has the potential in spades, especially with some series that leave the possibility open or even pointedly declare that it could happen.
** There's a general rule of thumb for all Kamen Riders: Unless stated otherwise, the Rider Belts can work for ''anyone''. Almost all the Kamen Rider shows have shown at least two people donning the same belt, with Faiz being the most memorable example, as all three main belts had a go at changing hands every so often.
** ''[[Series/KamenRiderKuuga Kuuga]]'' averts this somewhat. Yuusuke was the only rider in the show, but outside of the show, be it sequels or [[AllThereInTheManual stories related to the show]], there has been at least four other Kuugas. Two of which are from alternate universes, one of which now has his belt in Yuusuke's possession, and the last one, the one where the Sailor Earth potential kicks in, found a prototype belt.
** ''[[Series/KamenRiderAgito Agito]]'' explicitly says that all humans have the potential to become Agito, and even if they don't, there's always a G3 style suit lurking around. In fact, whatever happened to G1 and G2?
** ''[[Series/KamenRiderRyuki Ryuki]]'' had this in spades, the existence of Abyss (see below) adding even more to it, as it was possible that any of the massive number of Mirror Monster could become an Advent Beast for a new Rider.
** ''[[Series/KamenRiderFaiz Faiz]]'' had six riders taking six Greek Letters, leaving eighteen more. There was also a stageshow which featured Kamen Rider Alpha, Beta, and Gamma. The one downside is that, for the most part, [[spoiler:the wearer of the Driver has to be an Orphnoch. But that's okay, more potential to Sailor Earth it.]]
** ''[[Series/KamenRiderBlade Blade]]'' is the only one outside of ''Kuuga'' to mostly avert this, as all four suits [[spoiler:and the Joker]] of its {{Playing Card Motif|s}} are already taken. The Movie Riders had to share a motif, an artificially created card called Kerberos, so there's where the "mostly" come in. It's possible to have riders based off artificially created Undead/Cards.
** ''[[Series/KamenRiderHibiki Hibiki]]'' also has opportunity, giving existing character Akira the ability to transform into Kamen Rider Amaki, and other side characters becoming Oni. And there is more than one Takeshi branch and that they dated all the way back in Feudal Japan
** [[Series/KamenRiderKabuto ZECT]] was constantly producing new Zecters. All one needs to do is think of an insect.
** ''[[Series/KamenRiderDenO Den-O]]'''s Imagin are based off Fairy Tales, so it's possible for one to make one based off an unused fairy tale. Kamen Riders in that setting are mostly made by bonding an Imagin to the suit, so you can also plop a pre-existing Imagin to make a new Kamen Rider.
*** The Imagin Sieg was supposedly based on the story of ''SwanLake'', which actually had a black swan EvilTwin named Oderjean to the protagonist, white swan Odette - hence, [[http://i14.photobucket.com/albums/a323/aaronhong/Den-O%20Expanded%20Universe/KRDenOClawForm2.png this pic of Sieg's Evil Twin.]]
** ''[[Series/KamenRiderKiva Kiva]]'' has tons of lore waiting to be fleshed out, like the First Kivat.
** Interestingly, ''Series/KamenRiderRyuki'' gained a canon Sailor Earth in the form of Kamata/Kamen Rider Abyss, an original character made for ''Series/KamenRiderDecade'' who uses Mirror Monsters that were seen but not contracted in ''Ryuki''. [[spoiler:And for extra fun, he's '''also''' a Sailor Earth for ''Series/KamenRiderBlade'', being the Paradoxa Undead, which was named but never shown.]]
*** Also, ''Decade'' has Kamen Rider Kivala, empowered by a small, female Kivat-like bat-critter from the World of Kiva. She didn't ''operate'' in the World of Kiva, [[spoiler: being Natsumi and all]], but she's what a Sailor Earth looks like in canon.
*** There's also a plethora of Kamen Rider Decade/Diend clones out there that could grab up some remaining motifs, like a rider who can assume all the second riders' forms, etc.
** ''[[Series/KamenRiderDouble Double]]'' is super easy, as nearly any gaia memory (and thus, any rider or dopant) can be made out of ''[[SerialEscalation any noun]]''.
** ''[[Series/KamenRiderOOO OOO]]'' had three Black Core Medals which were not used by Eiji. Several fan-art created what would happen if Eiji used them for a combo. It's also very easy to make up entirely new sets of Core Medals: Just choose three animals that fit a theme. Rarely there are fan-created Greeed or even Kamen Riders ([[Film/KamenRiderXKamenRiderFourzeAndOOOMovieWarMegaMax Maybe both]]) to go along with new medal sets. As for full-fldged Rider powers, that's simple; since the Kogami Foundation made their own Riders (Birth and Aqua) in-canon after studying Medals, that opens the door for fanfic writers to do the same.
** ''[[Series/KamenRiderFourze Fourze]]'' is perhaps the only Heisei era rider that has little to no exploitable template like the other Riders do, since the only three riders seen in the show are the main rider, the secondary rider (which is based on a different sort of powerset than Fourze's), and a movie-exclusive rider who cloned herself off Fourze.
** ''[[Series/KamenRiderWizard Wizard]]'' spells out what needs to be done to gain magical powers: someone needs to have magical potential in the first place, hit a DespairEventHorizon and cause that latent magic to form a monster called a Phantom, and then regain and hold onto hope quickly before the Phantom takes over your body and kills you, leaving it SealedInsideAPersonShapedCan. After that, there's just the matter of getting the belt and rings to go with it, which usually came from the White Wizard in-series. Or you can do what Kamen Rider Beast did and obtain a belt with a Phantom pre-sealed in it. In any case, one of the major bits is to choose a mythological creature to base your Phantom off of, as that usually influences a character's Rider form.
** ''[[Series/KamenRiderGaim Gaim]]'' manages to set up a formula right as it premieres. Take a fruit/nut (i.e. Orange), take a kind of warrior (i.e. Samurai) and mash them together to make a Gaim Rider. There was originally a problem of ''how'' they get their hands on a Sengoku Driver, but midway through the series they started being mass-produced (if not distributed yet).
** Monsters in the Kamen Rider franchise are easier to make. Especially with the Heisei era Kamen Riders, in which one can just select an animal motif that wasn't used before in that show. There are a few exceptions (like the Worms having only insect motifs, and rarely crustaceans, the Imajins, Zodiarts, and Phantoms needing to be based off a fable, constellation or mythological creature respectively), but the largest exception is, again, Blade, in which all 52 monsters are accounted for, though not all of them have appeared in the show, like the Stag Undead. However, it's easy in Double, where one just needs to think of a noun, and bam, instant Dopant.
** Some Rider series also make it easy for new forms to be created, especially with the later Riders with the exaggeration of MerchandiseDriven {{Transformation Trinket}}s.
*** Kuuga? His forms all came to be because Yuusuke was thinking "I need to be able to do X!" and when it got ''really'' desperate, his suit turns a new color, gains a power... [[MultiformBalance and loses one]]. To come up with new forms for him, you only need to think of a color that hasn't been used. (Red, white, blue, green, purple, black, and now gold - Decade does it again! - are taken. ''Anything else goes.'' You can also give "Rising" upgrades to your new forms, and give "Amazing" upgrades to new ''and old'' forms - if there's Amazing Mighty, why ''not'' Amazing Titan? ''[[SerialEscalation Amazing Ultimate]]?'')
*** Den-O? Just add another Imagin, original or existing.
*** Double? You don't even have to invent new memories from whole cloth. What if Philip and Shotaro used another Rider's Gaia Memories? Or even Dopant Memories? Nazca and Skull are pretty popular choices for those [[spoiler:and Accel is even teased in the show, having Shroud's intention being to fuse Accel and Double's powers together]]. Canonically speaking, however, the existence of alternate Fang combos was effectively {{Jossed}} by the Double novel, where it's explained that Shotaro's compatibility with the Joker Memory lets him put a leash on Fang's berserker tendencies; any other combo would result in Double becoming uncontrollable.
*** OOO? Core Medals can come in any animal motif, and the show even has created several that fall outside of the 21 Core Medals.
*** Also, Fourze introduces new Astro Switches via the "Hey, look what I whipped up today!" method, so new attachments for him can be easily introduced. However, there's a catch and it's established that there's only 40 Switches, all of which are accounted for, and the others are either useable by TheRival (Meteor and Meteor Storm Switches), abnormalities (Super Rocket and Super Drill Switches), or toys with little to no purpose in the show (Rider Switches).
*** Same with Wizard, except for rings and that there's no limit.
*** As mentioned above, Gaim has potential in spades; just [[http://en.wikipedia.org/wiki/List_of_culinary_fruits pick a fruit]] and pair it with an armored warrior and weapon motif and you're done.
* Used to be common to insert a new survivor into ''Series/{{Lost}}''. In fact, the ''show itself'' inserted two entirely new crash survivors into the plot during season 3, linking them to several significant events in their sole flashback. Not so common after seasons 5, which [[spoiler:killed off every survivor that wasn't a main character, Rose, or Bernard.]]
* ''CuteyHoneyTheLive'' has three girls based on three suits of cards. You can easily come up with a new one to represent clubs. In fact, the ''two other protagonists'' are a canon example of this: Honey's always had heart designs, but interpreting it as the ''suit'' hearts and coming up with diamond and spade girls with the same power is new.
* While this didn't really work during the show's run, the ''Series/BuffyTheVampireSlayer'' finale created hundreds of Slayers around the world. As a bonus, Slayers are always teenage girls (except for those who manage to make it to their twenties), and as MostFanficWritersAreGirls...
** ''Series/{{Angel}}'' firmly established that the Slayer being the sole warrior for humanity was a load of poppycock, with numerous individuals and organisations working against (and for) "vampires, demons and the forces of darkness", creating massive fanfiction potential.
* With the introduction of a Magic School in ''Series/{{Charmed}}'' season 6 this opened up mountains of possibilities for fanfic writers to create teenaged witches who fight demons. Using additional Elders, Avatars and other such beings is quite easy too since only a handful of them received names on the show. Also due to the show's FantasyKitchenSink nature, plenty of fanfics introduce foes based on mythological creatures the show didn't use - a German "season 9" fanfic used Avalon, the Gorgons and the djinn for example.
* Happens many ways in ''Series/DoctorWho'' fics:
** In classic series fics the Doctor would run into any amount of former classmates and Time Lord renegades who nicked their own TARDIS and legged it, semi-justified as it often happened in canon with the Rani, the Master, Drax, the Monk, etc.
** In new series fics the introduction of the Chameleon Arch allows for any amount of Time Lord survivors hiding in the local populace.
** In fics for both eras the Doctor would land the TARDIS and pick up a totally-not-a-self-insert-at-all new companion.
** For the vast majority of episodes, the only regulars are the Doctor and his one-to-three companions, featuring otherwise entirely new casts. Fanfiction can and has easily followed this formula.
** During the Wilderness Years, Ninth Doctors were quite fashionable. Some ''canonical'' examples include the Ninth Doctor played by Richard E Grant, the one played by Nicholas Briggs, the one Virgin tried to create 'played' by David Troughton, the Doctor from the Honore Lechausseur series who smokes and wears muttonchops, the Doctor used in some Short Trips stories who has an aging apolitical hippie aesthetic (wearing a camel coat and lots of pachouli), and the Doctor played by Rowan Atkinson. And those are just official and semi-official examples - the fandom took it in even madder directions.
* Many ''{{Glee}}'' writers have yet to realize that adding a thirteenth member to New Directions throws off number balances, as there is usually an even split between boys and girls ([[SixthRanger Jesse]] didn't help that lesson sink in much either, even taking into account that his stay was temporary).
** Do what they did in Season two: get rid of Matt Rutherford.
** Season 2 ended with them having 13 members, but then again Blaine can act as a counterbalance despite being in a different school.
** At the end of season 3, they have 16 members, though 8 of them graduate.
** There's also an indeterminate number of nameless, faceless Troubletones girls.
** Thanks to ''Series/TheGleeProject'', many fanfic writers can cast contenders that didn't win as their [=OCs=], which more often than not are usually just the contestant with a different name (sometimes not even that) and slightly more [[GuyOnGuyIsHot hetero]][[GirlOnGirlIsHot flexible]].
* ''Series/{{Supernatural}}'' has had a specific brand of this since pretty much the beginning of the show: the sister-fic. Just make up a name and give her a reason why she wasn't seen in canon up until that point (hidden by John for safety, taken by demons because she's psychic like Sam, etc.), and boom! You have a female Winchester. Never mind the logical quagmire she often creates--how can she be younger than Sam, but still be Mary's daughter? Why would John let one child live a normal life, and not all of them? Some writers try to avert this by just making the fic an AU where she's always been there, and is very frequently Sam's twin. Usually, the new sister ends up being a MarySue, and the stories are just rehashes of episodes where her presence makes everything better. Another common occurrence in the Supernatural fandom is to create one or more new hunters, often a set of sisters. In the Supernatural universe, this isn't impossible, since hunters exist across the world. While some people create interesting additions to the universe, most are blatant self-inserts, especially because if these characters are female, the boys seem to fall for them by the end.
* Every now and then, ''Series/CriminalMinds'' will mention other, unseen [[TheProfiler BAU]] teams. One of them actually was showcased in the Season Five episode ''The Fight'', which became the team for the short-lived spinoff ''Series/CriminalMindsSuspectBehavior''. Another was the JTF-12 team- featured as the targeted victims of the Ian Doyle arc of Season Six- of terrorist profilers that Emily Prentiss was a part of before joining the BAU. And the number of agents in the BAU isn't hard-coded, meaning creators could create another agent to join the team. Care must be taken to ensure the new agent fits in with the team and everyone has their proper roles storywise, as the [[LoadsAndLoadsOfCharacters cadre of characters]] can get confusing for the audience if handled improperly.
* There are said to be 127 Elements in ''Series/SapphireAndSteel'', of whom four appear in the televised canon and two more in audio adventures. This leaves ample opportunity for fan writers; they need only pick the name of an element, gemstone or alloy that hasn't appeared in the show, and endow them with appropriate characteristics and powers.
* Being a prison drama, all you really need for an original character is a crime for them to have committed, but the ''Series/{{Oz}}'' equivalent of Sailor Earth is usually the first or only woman in Em. City (bonus if she's allowed because one or more of the other prisoners promises to protect her, and was wrongfully convicted, whether because she's actually innocent, or because she murdered a rapist. Bonus points if the other prisoners agree to protect her ''because'' they think she shouldn't have been found guilty.
[[/folder]]

[[folder:Music]]
* Neither Earth nor Pluto appear in Gustav Holst's ''Planets Suite;'' Pluto hadn't been discovered yet, and Earth was, from Holst's astrological perspective, insignificant. Some amateur composers have created music to fill in these two gaps.
[[/folder]]

[[folder:Professional Wrestling]]
* The most common plot trope in wrestling fics in the last few years is the introduction of a new WWE Diva (or in some very rare occasions, a new male wrestler). Understandable as there are always wrestlers coming and going. Either the girl is a legitimate fighter trying to be the second coming of Chyna and bring credibility back to the Divas division, or she's there to be the romance object of a male wrestler (the members of the Shield have been very popular targets lately). Often, these new wrestlers are the children or younger sisters of an current star.
** Sometimes, they vary the formula by having the new girl be a makeup artist, wardrobe girl, or a member of the tech crew.
[[/folder]]

[[folder:Tabletop Games]]
* This is outright encouraged by ''TabletopGame/{{Warhammer 40000}}''. Want to make up your own Space Marine chapter? There's canonically a thousand of them, and only a hundred or so have been so much as mentioned in canon, so go on ahead-- it's even perfectly valid to imitate an existing army due to the way successor chapters are created. There are also two Primarchs whose identities and abilities are unknown, seemingly for this trope. Similarly, there are a million worlds in the Imperium that your homebrew Imperial Guard regiment could originate from, the Eldar are so secretive that a previously unheard-of Craftworld suddenly appearing wouldn't be out of place, and the Tau are always settling new Septs. And so forth for Dark Eldar Kabals, Tyranid Hive Fleets, Ork tribes, Necron Tomb Worlds, Chaos Space Marine warbands... there's always far more of them than are ever actually detailed, and there's no shortage of players willing to make a neglected bit of background their own.
** The Chaos Codex takes this concept UpToEleven. Not only can you invent your own renegade chapter, you can also mix and match various legions and chapters into one army, with the justification that they are all united under one banner for some cause or another. This was originally the concept for the Red Corsairs, before they had their combat doctrine retconned.
** One of the biggest reasons why the 5th-6th edition ''Codex: Space Marines'' fluff by Matt Ward was hated was because it discouraged this, claiming that any chapter that wasn't just like the Ultramarines was bad.
** Matt Ward also, ironically, gave the Necrons more character by retconning their backstory so that each individual Tomb World had more characterization to it rather than just have a different color scheme. Previously all were controlled by the C'tans and had little free will, meaning that, apart from the paintjob, they were more or less identical (although that was sort of the point).
* Similarly, the same is encouraged to a lesser extent in {{Battletech}}. While pretty much all of the House regiments and Clan formations have been detailed in canon, Catalyst flat-out encourages players to make up their own new mercenary units and other formations.
* ''{{TabletopGame/Exalted}}'' recently made room for not one, but ''two'' separate Sailor Earth Exalt types in their recent Alchemicals splatbook. Not only did they open the possibility of Exalted with a natural affinity for [[PowerCrystal Adamant]], they also said that the Abyssal Exalted are [[TheUnchosenOne a mistake]] and not intended, leaving it open for a new Exalt type who has a "true" affinity to [[PoweredByAForsakenChild Soulsteel]]. These two types are only mentioned as vague possibilities--nothing to suggest what they should be, if they exist. It was suggested in Dreams of the First Age that slain Incarnae existed once, and their Exalted went mad and were wiped from existence; this is one potential explanation of the above. However, given the source and given that it is generally considered to be quite feasible--if far from easy--to take on one's almighty divine patron and ''[[DidYouJustPunchOutCthulhu win]]'', the fan base has reacted to this idea with little approval.
** Perhaps a better idea would be to have the concepts they attuned to be one of the casualties of She Who Lives In Her Name's [[CosmicRetcon Three Spheres Cataclysm]]. These lost shards can only attune to people who embody, say, Flarg, but since no one can Flarg, these Shards are sadly not able to Exalt their chosen.
** On the Terrestrial side, while canonical Dragon-Blooded can only be aspected to the five Gaian elements (the big four, plus wood), it's a common hobby to try to make Dragons of the five Underworld elements (ash, bone, pyre flame, blood and void] or the six Autochthonian elements (crystal, lightning, metal, steam, oil, smoke).
** Also for the Abyssals, the sourcebook says there are thirteen Deathlords, but only nine of them are described and given stats. This is explicitly so that Storytellers can create their own Deathlords.
* Since every {{Splat}} in the ''TabletopGame/NewWorldOfDarkness'' can have [[PrestigeClass more-specialized splats]] (Bloodlines in ''TabletopGame/VampireTheRequiem'', Lodges in ''TabletopGame/WerewolfTheForsaken'', Legacies in ''TabletopGame/MageTheAwakening'', etc.), it's painfully easy to crank out a new collection of Bloodlines, Legacies, etc., every couple of months. One book was even a collection of fan-created bloodlines.
** This isn't new for White Wolf; the TabletopGame/OldWorldofDarkness usually included some form of lost group. In ''Werewolf'' it was the White Howlers, ''Vampire'' had the Cappadocians, and in ''TabletopGame/ArsMagica'', something of a predecessor to ''TabletopGame/MageTheAwakening'' before its Dark Ages book came out, it was House Diedne, all mentioned but not present in the setting. It's a Sailor Earth player's field day.
*** House Diedne is also mentioned in Mage: The Ascension as a failed experiment between the Order of Hermes and the Verbena. There's also the rules for creating new bloodlines in ''Vampire: The Masquerade'', the different "lesser" Mage factions, the Siberakh werewolves (Shadow Lord/White Howler hybrids) and all the other werebeast species (cats, snakes, spiders, etc.), and so forth... (And don't even mention hybrids like Abominations (vampire werewolves)).
* In a crossover with literature, it seems like almost every group of ''TabletopGame/TheDresdenFiles'' RPG has an Autumn Knight. Not spring, always Autumn. Additionally, in the series there are three main vampire courts. The Black Court, the Red Court, and the White Court. A Jade Court has been mentioned in passing, and Billy brings up the possibility of there being different colored courts.
* The original ''Lost Worlds'' gamebooks (and it's Japanese twin series ''QueensBlade'') has this in spades, since the original LW books (and the first QB ones) [[ExcusePlot didn't have a detailed plot]] beyond (at least in the QB case) the aforementionated tournament, so you can create any girl from any classic fantasy species (humans, elves, dwarves, etc) as long that character is a female and sometimes that rule is not ''always set in stone''. (Since it's implied the ruling queen or the gods can change the rules if they want it).
** And now with the ''Queen's Gate'' gamebooks, you can include any girl from any kind of universe, regardless how much advanced is her technology or her culture from the rest of the cast.

[[/folder]]

[[folder:Toys]]
* ''Franchise/{{Bionicle}}'' has plenty of humanoid species where only one or two named characters exist, and in order to expand on the main Toa cast all you need to do is choose any of the ElementalPowers, add a MaskPower and a weapon with optional attribute. Or, you could try your hand with the numerous Dark Hunters, which are already a mixed bag of various species, powers and motives.
** The same applies for pretty much everybody in the ''{{Bionicle}}'' canon.
* For ''HeroFactory'', the successor line to ''Bionicle'', {{LEGO}} created the Hero Recon Team. In-universe, the Recon Team is an intelligence force keeping tabs on the locations of villains. Out-of-universe, it's a program that lets fans create their own in-canon original characters and [[MerchandiseDriven buy toy versions of them]].
** Sadly, you can no longer purchase the figures. It is now simply a watered down creation tool, like the designer software.
* ''Franchise/MonsterHigh'' is also littered with fan characters. All one has to do is think of a famous monster, then come up with their offspring's profile. The trouble is, fans have a hard time telling appropriate uncanonical monsters (like, say, selkies or harpies) from more figurative monsters (like [[{{Saw}} Jigsaw]] or ''[[TheSilenceOfTheLambs Hannibal freaking Lecter]]'')...
* ''Franchise/EverAfterHigh'' has tons of fan characters too, done in the same way as the above. Most common are original characters for famous fairy tales that don't have canon EAH characters (especially ones made famous by Disney - ''Literature/BeautyAndTheBeast'' and ''Literature/TheLittleMermaid'' are especially popular). ''Literature/AliceInWonderland'' original characters also pop up frequently due to several canon characters, as are ones for ''Literature/TheWonderfulWizardOfOz''. There are also [=OCs=] for more obscure fairy tales by Brothers Grimm, Hans Christian Andersen, and Charles Perrault, and even a few original characters for stories by more obscure fairy tale writers such as Madame d'Aulnoy and Andrew Lang.
** Disney-based [=OCs=] run rampant, and they are ''despised'' by much of the fandom, especially when the character designs closely resemble the Disney character. The worst offender has been ''Disney/{{Frozen}}'' - daughters of Elsa have popped up frequently. Other offenders include characters based on ''Disney/{{Pocahontas}}'', ''Disney/ThePrincessAndTheFrog'', and ''Pixar/{{Brave}}''.
** Among the plethora of fan characters are plenty based on darker fairy tales, generally created by members of the PeripheryDemographic.
* The original Toys/LEGODinoAttack line was simply about four guys fighting mutant dinosaurs. ''Roleplay/DinoAttackRPG'' added a full 237 additional agents, and that's just for the Dino Attack team itself. Other areas that lent themselves well to original characters included Franchise/LEGOAlphaTeam, Toys/LEGOAgents, Toys/LEGOPirates, and more, with each theme also getting its own slew of [=OCs=] in its respective {{Play By Post Game|s}}.
[[/folder]]

[[folder:Video Games]]
* Countless numbers of new Freedom Fighters in ''Franchise/SonicTheHedgehog'' fanfiction. This is easier in fanfic concerning the [[ComicBook/SonicTheHedgehog Archie comic]] series, as there are any number of unnamed Freedom Fighter groups to work with. The issue comes when people shoehorn their new character into the existing groups, or if they somehow solve everything...
** Back when Knuckles was said to be the LastOfHisKind, multiple Mary Sue echidnas would show up with the explanation that ''she'' thought she was the last of her kind, or she came from another dimension, and so forth. This has pretty much stopped now that Knuckles really isn't the last of his kind anymore in most of the various canon universes.
*** Boy, when they played [[spoiler:''VideoGame/SonicChronicles'', they'd probably have been shaking with rage or thinking "oh, s/he came from this dimension where all the echidnas are." (Remember Shade?)]]
** Heck, many Sonic fan characters [[InNameOnly have nothing to do with the series at all]].
** There are plenty of never-before-seen hedgehogs who carry around an ''eighth'' Chaos Emerald running around.
** More than a few fancharacters were created by Professor Robotnik on the ARK as "backup ultimate lifeforms".
* In ''VideoGame/MegaManX'' fanworks, new characters are most often created as Maverick Hunters, like the canon protagonists. And since X is part of the 17th Unit, that frees up at least 16 other units of indeterminate size for fan usage.
** There's also characters who are either the "real" last creations of Light or Wily, or prototypes of X or Zero, and were also sealed away in a capsule until discovered, and the most Sue-ish of which tend to have caused the "Cataclysm," the by-now {{Jossed}} Fanon theory that got rid of the Classic series characters.
** The original ''VideoGame/{{Mega Man|Classic}}'' series easily allows for new Robot Masters or other new robot characters, who have [[ThemeNaming musical pun names]]. The ''VideoGame/MegaManX'' series simply uses animal names to get the same result.
** In a similar vein, new scientists tend to come up, thanks to the series having so few of them (Drs. Light, Wily and Cossack). Occasionally, some of them do follow Cossack's [[ThemeNaming musical naming theme]].
** It's also popular in the series to do this with Proto Man, whose infrequent appearances in the canon mean there's plenty of spaces for fanfic writers to fill in for him.
** Since X and Zero are the leaders of the 17th and 00th units respectively, it's also common to create new characters to make up these units and show them functioning as teams. And ever since ''[[VideoGame/MegaManXCommandMission Command Mission]]'' showed that the Maverick Hunters have multiple ''headquarters'', like the East-Asia HQ shown in the game, opens up even ''more'' opportunities for other units.
** ''[[VideoGame/MegaManBattleNetwork Battle Network]]'' isn't hard to do this to either, being as there are several Classic Robot Masters and other robots that went unused by the end of the series, and ''5'' and ''6'' bring in Colonel and Iris and opening up possibilities for ''X'' series-based [[{{Expy}} Expies]]. That's not even counting the possibility of random officials and/or other Netbattlers and their Navis made up wholesale, or giving an operator to [[KillAllHumans Bass]]. This can also work in reverse, as both ''Battle Network'' (''[[Anime/MegaManNTWarrior NT Warrior]]'' included) and ''[[VideoGame/MegaManStarForce Star Force]]'' have introduced [=NetNavis=] who do not have a canon Robot Master counterpart in the original series. On top of this, one Navi (Ring.EXE from ''[[GaidenGame Battle Chip Challenge]]'') is [[DistaffCounterpart the opposite gender]] of the Robot Master they're based on (Ring ''Man'' of ''[=MM4=]''), opening up yet another door. As the ''[[VideoGame/MegaManLegends Legends]]'' series demonstrates, it doesn't stop there either: at least one Navi is influenced by a ''Legends'' character [[note]]Glyde.EXE, based on Glyde from ''[=MML2=]''[[/note]] and no less than four other characters have cross-series counterparts between ''Battle Network'' and ''Legends'' [[note]]Shu and her brothers Appo and Dah (''Legends 2'') > Shuko Kido and her brothers Atsu and Ty (''[=BN4=]: Blue Moon'' and ''[=BN6=]: Falzar''); Yaito of Pokte Village (''Legends 2'') > Yai Ayanokoji; additionally, Dr. Wily has another counterpart in the form of Wily, the Uptown boat house owner in ''Legends''[[/note]].
* ''Franchise/KingdomHearts'':
** Organization XIII often acquires a 14th member in fanfiction, to be paired up with one of the other members. These fanfics probably contributed to the annoyance of much of the ''Kingdom Hearts'' fandom when it was announced that there actually would be a 14th member in a later game. The only real challenge to this is if the character sticks to the naming scheme, which is an anagram of the Nobody's real name with an X thrown in.
** The canon "14th member" is an interesting case: she's [[spoiler:a DistaffCounterpart of Sora that resembles Kairi, wields the Kingdom Key, and becomes a close friend to both Roxas and Axel. She is revealed to be just a conglomerate of some of Sora's stray memories (which he can't wake up without): when she realises this, she goes on the run and is determined useless by the higher-ups. She ends up committing [[SuicideByCop Suicide By Roxas]], and is absorbed into him, along with everyone's memories of her life. The final [[PlayerPunch punch]]: her name is Xion, which follows the naming convention for "No. i" - as in an imaginary number, showing the contempt in which her creator, Xemnas, held her.]] That has got to be a TakeThat on behalf of the developers.
** New keyblades get handed out like lollipops in the ''KH'' fanfic 'verse, so Sora and Company start running into new worlds and new Keyblade masters with such alarming frequency that you have to wonder how the original worlds were even lost in the first place. However, the series states that once there ''were'' thousands of Keyblade wielders, and more do keep popping up, so there's precedence for this.
** Some fanfics of ''Kingdom Hearts'' may actually show an ''entirely'' new Organization surfacing from all that was ever left of the old one. Considering the "Twenty Years later, a new disaster causes a group of people to lose their hearts and create nobodies"-situation is, in theory, highly possible....
*** [[spoiler:And much as with the above two examples, this is entirely canon. ''Dream Drop Distance'' states Master Xehanort is reviving Organization XIII using himself as the leader and various incarnations of himself and other beings corrupted by him as the members.]]
** Chances are you'll find new types of Heartless and Nobodies in fanfics. Given that most of the Nobodies are based on a ''Franchise/FinalFantasy'' job class in name and abilities, creating new types is fairly simple. Besides, it is strongly suggested that there were five more classes of Nobodies that were never seen. Ten types of Nobodies were in ''Kingdom Hearts II'': two common types (Dusks and Creepers) and one type of minion for each of the eight Organization members still alive at the beginning of the game. There is no logical reason why the five who were killed at Castle Oblivion wouldn't have had their own minions.
* ''VideoGame/RatchetAndClank'' is so loosely written in canon with any number of worlds and characters that he can encounter in any given game that it's a given that you'll have to invent a couple characters. But any OC that pops up as a Lombax is an automatic Sailor Earth! Strangely, the majority of Sues in the fandom are either humans or humans-turned-Lombaxes, so...
* In VideoGame/{{Portal}} fics there is no efforts in finding space for an OC to come from, what with the thousands of test subjects, scientist, and robots who work at Aperture. Now having them survive the events of the second game is a bit trickery but still easily manageable. Its not hard to imagine someone other than Doug Rattman escaping and laying low in that facility or stay asleep in some forgotten cryogenic pop, (its completely within Aperture's character to lose someone like this). It was also popular for [=OCs=] to come from [[spoiler: those humans you find in the Cooperative campaign, until the DLC revealed that GLaDOS killed them all]] Then there all those other dimensions.
* As noted in General, it's trivially easy to add a "baddest of the {{badass}}" [[CoolSpaceship new ship]] in any game or series based in space, particularly when there's such a potentially huge war zone where only relatively small slivers of it have been revealed, like in the ''VideoGame/WingCommander'' or ''StarWars'' game universes.
* While there were about 30 [[SuperSoldier Spartan-IIs]] in the ''Franchise/{{Halo}}'' universe, less than half of them have been named so far. This makes creating a new Spartan character as easy as picking a first name and a three-digit number. Just don't expect your Spartan to make it past the [[EverybodysDeadDave fall of Reach]] -- every survivor of that battle is canonically accounted for. Of course, in-universe Spartan casualties are [[NeverSayDie labeled MIA and never KIA]]... [[HesJustHiding You know what that means]].
** There is however the Spartan-[=IIIs=], hundreds of which were produced, [[NormallyIWouldBeDeadNow a handful of which survive]] their [[LaserGuidedTykebomb first and only major deployment]], whom almost no one knows about due to [[{{Masquerade}} an extensive ONI coverup]]. It could be argued that ''Ghosts Of Onyx'' was written with the intention of expanding the unfilled roster to allow more Spartan-centric stories to be written.
** And as it turns out, the fact that there was only one class of Spartan-[=IIs=] has since been retcon'd away, so people can make Sailor Earths of them all they want.
** And now we have the Spartan-[=IVs=].
* In the ''VideoGame/{{Touhou}}'' canon, {{youkai}} apparently outnumber humans by a fair margin. If the sheer diversity of ''those'' in Japanese mythology isn't enough fodder for the fans, races like the Celestials, the Yama and the Kappa only have one named representative ''each'', allowing fans free rein to make their own. Of course, the franchise has the unique distinction of being largely {{Fanon}} anyway.
** Why limit ''Touhou'' [=OCs=] to ''Japanese'' mythology? Canonically, the vampires, psychically-produced poltergeists, resident CuteWitch, and fairies all have strong Western influences, and there [[EpilepticTrees may or may not]] be a Chinese dragon in the mix as well.
** This isn't even limited to youkai. Aside from Keine, Akyuu and Kosuzu none of the residents of the Human Village are known (and those two aren't exactly human anyway), and it's canon that humans from the Outside find themselves in Gensoukyou on a semi-regular basis. The latter in particular is incredibly fertile ground for {{Self Insert Fic}}s.
** It's also notable that Touhou characters often have absolutely [[SuperpowerLottery absurd powers]], making it paradise for someone who wants to create a superpowerful character without abusing canon too much. [[PersonOfMassDestruction "Destruction of anything and everything"]] and [[RealityWarper "manipulation of boundaries"]] are legit powers. Honestly, the more ridiculous your character's power is, the better. Bonus points if it sounds innocuous at first but turns out to have ludicrous applications.
** Some of the fan-produced characters have acquired such a popularity that they might as well be canon. Notably Mitori Kawashiro, the sister of the Kappa girl Nitori, whose power is to prohibit anything (in good Touhou fashion, this is difficult to wrap your head around and potentially absurdly broken). Mitori has her own fanmade theme and appears in a fanmade game.
** Another relatively popular fan character is the Sendai Hakurei no Miko (The Previous Generation Hakurei Shrine Maiden). Originally a ''VideoGame/{{MUGEN}}'' Touhou character who was notable for being a pure close-range physical fighter (even when compared to Hong Meiling) among the cast of long range projectile fighters, artists and writers picked her up and fleshed her out as a no-nonsense shrine maiden who prefered to beat her opponenets to the pulp with her own fists, as a result sporting a modifed Miko outfit with a LeotardOfPower that shows off her [[CoveredInScars scar-covered body]]. Her relation to Reimu varies, from Mother to a distant Ancestor, or just an unrelated woman who previously held the the position of the Hakurei Shrine Maiden.
* ''VideoGame/{{Persona}}'' fanfics will probably involve someone else learning to use a Persona. Or another member of [[VideoGame/{{Persona 3}} SEES]]. Or an employee of [[VideoGame/{{Persona}} SEBEC]]. Or another member of [[VideoGame/{{Persona 2}} the Masked Circle]] or who survived [[VideoGame/{{Persona 4}} the fight in the TV]].
* ''Franchise/TheLegendOfZelda''-fanfic writers frequently invoke this trope:
** Remember the UrbanLegendOfZelda that there's actually a fourth [[MacGuffin Triforce]], which balances and completes the other three? This (very unlikely) theory is often taken as premise for fanfiction and along comes a fourth golden goddess ''and'' a fourth triforce-bearer, usually female, SoBeautifulItsACurse and related to Link in some way. Or the fourth triforce goes to an AuthorAvatar, who was [[TrappedInTVLand "sucked into the game"]], another very popular premise in the world of ''Zelda''-fanfiction. For a ''"good"'' example of this, see ''FanFic/MyInnerLife''.
** There's also "Kasuto" in ''Ocarina of Time''. To elaborate, every town in ''Zelda II'' had a character in ''Ocarina'' named after it, with the exception of Kasuto. This has occasionally overlapped with the fourth Triforce bit.
** On the subject of the fourth goddess bit, it turns out in ''Skyward Sword'' that there ''is'' a fourth goddess. Of sorts, anyway. When the golden goddesses of old departed from the world they created, they entrusted the Triforce to a goddess named Hylia for safekeeping. However, while Hylia is a revered and powerful deity, she is depicted as being of a lesser status compared to the likes of Din, Nayru, and Farore.
** Strangely, very few authors take the obvious path of using the canonically unidentified person who would get the Triforce of power if Ganon didn't keep stealing it.
* ''VideoGame/TeamFortress2'' [=OCs=] tend to come in the flavor of the (currently nonexistent) "tenth class" or as the First Female [Class]; most of the writers don't bother to address the ValuesDissonance that most, if not all, of their prospective teammates would have 1960s sensibilities. Of course, there's the other idea with regard to ''[=TF2=]'' [=OCs=] in that the classes are used as templates and original characters are laid over them. This is seen in ''Webcomic/CuantaVida'', where there can and have been two members of one class with entirely different personalities.
* This is very common in ''VideoGame/Left4Dead'' fanfic, as many writers create a new Special Infected which makes the Tank look like a Muscular Chipmunk, or adding a 'survivor' who caught the Green Flu only to gain all the superpowers and none of the flesh-hungering side effects (the ''only'' precedent for this sort of thing in-canon is that the playable Survivors can take absurd amounts of damage - at least below Expert difficulty - and are themselves carrying TheVirus). Alternatives include fleshing out the unseen characters of "Chicago Ted" or "Keith", since there is literally nothing canon revealed about either of them, other than that the former is apparently "king of the zombies" and the latter [[NighInvulnerability has already survived several absurd predicaments]] ''before'' said virus was introduced).
* ''Franchise/SuperMarioBros'' is subject to this, due to how little several settings or groups are featured or elaborated upon, mostly Bowser's troops. Specific examples include:
** Sarsaland. The Mushroom King. Beanbean Kingdom. The Shroomers. More plumbers. Worlds 1 through 8. The Yoshis. Subcon. It's really too easy. The world building is there, we're just not given all of it.
** It's common for someone to create a whole team of ''VideoGame/PaperMario'' partners. Simply dress up some of the series signature mooks (Goombas, Koopas, Boos, maybe throw in a Toad or Yoshi or original creature in there), make sure they have the ability to explode, jump gaps, disappear, etc., and a new team is set.
** It is given some elaboration in ''VideoGame/YoshisIsland DS'', which states that there are a total of seven people as powerful as Mario and Luigi, and they're all named. That doesn't stop anyone.
** Creating a SixthRanger for the [[VideoGame/SuperMarioRPG Axem Ranger]] to follow the [[Franchise/SuperSentai pattern they are]] [[Franchise/PowerRangers a parody of]] is also common. Usually Blue, Pruple isn't unheard of though. In one example [[SixthRangerTraitor the Axem Blue turned out to be Geno]].
* It's easy to add pretty much anyone into the ''SilentHill'' Universe without major canon issues, so you can expect that a lot of those people are going to be self-insert/wish fulfillment characters, or outright angsty {{Mary Sue}}s.
* ''Very'' easy to do in ''VideoGame/DragonAgeOrigins''. Despite that the box says the main character is among the last Grey Wardens, Alistair mentions this is only true in Ferelden, the game's setting. Speaking to him brings up the mention that there are Grey Wardens all over the world and in neighbouring countries - a Sailor Earth could simply be from another part of the world. ''Ridiculously'' easy to do for an ElsewhereFic. Indeed, the expansion pack, ''[[VideoGame/DragonAgeOriginsAwakening Awakening]]'', uses this very setup - if you choose to start a new character rather than import the hero from ''Origins'', they will be a senior Warden from Orlais sent to help replenish the ranks of the Grey Wardens in Ferelden.
* In ''VideoGame/{{Borderlands}}'', a Sailor Earth could simply be another vaulthunter like the four playable characters, complete with a new gadget, power or physical ability. Better yet, it could be an entire team of four new vaulthunters, as they always seem to travel in groups of four. Bonus points if one member is one of the 5-6 other "Sirens" like Lilith and Maya.
** Other possibilities involve creating new characters tied to the prolific weapon manufactures found in game.
* ''Franchise/MetalGear'' has the three Snakes: Solid, Liquid, and Solidus. The absence of the most obvious third entry in the [[ThemeNaming matter-based naming cycle]], Gas Snake, makes him an easy choice for this. Plasma Snake would be a somewhat close second. However, Solidus Snake fills the theme roll of Gas Snake.[[note]]Solidus is a chemical term for the line on a pressure/temperature diagram that marks the phase transition between a solid and liquid.[[/note]] [[TheLastDaysOfFoxhound Bose-Einstein Condensate Snake, however, has not had much support.]]
* The general concept of Council Spectres in ''Franchise/MassEffect'' alone is ripe for this trope. Outside of Shepard, Nihlus, Saren, Tela Vasir, Jondum Bao, and [[spoiler:either Kaidan Alenko or Ashley Williams, depending on who you let live in the first game]], the Spectres in general have been ''barely'' given any attention in game or in the ExpandedUniverse, with the exception of [[AscendedMeme Blasto, the first Hanar Spectre]].
** The various merc groups and even C-Sec employees offer more options for this trope, too.
* Fan characters in both ''Franchise/SpyroTheDragon'' canons are popular, ranging from simply other dragons to another survivor of Spyro and Cynder's Year of the Dragon. Other popular topics are a Wind Guardian or a replacement for [[spoiler: Ignitus]], as well as Purple Dragons between Malefor and Spyro.
* ''VideoGame/DissidiaFinalFantasy'' is an IntercontinuityCrossover bringing together thirty ''Franchise/FinalFantasy'' characters from all over the series to fight on behalf of the gods Cosmos and Chaos. ''Dissidia'' and its prequel ''Dissidia 012'' explain these wars occur as a cycle--when one side loses they get their memories of the battle erased, and are revived to fight again. The two games cover the 12th and 13th cycles, and the 13th one of the last. That leaves Cycles 1-11 unseen, with no real information on who was fighting in them, for which side, and what happened that they didn't make it to future cycles. As a result it's common for fanfiction to be set in one of those earlier cycles with new characters drawn into the war, and from there you can take the story pretty much anywhere you want it to go.
* A very easy way to make a ''Franchise/MortalKombat'' fan [[XtremeKoolLetterz kharakter]] would be to take a kolor that ''hasn't'' been used by a ninja yet, and make your very own HighlyVisibleNinja for that kolor.
* Apparently, [[VideoGame/{{Doom}} new varieties of hellspawn from]] [[FanNickname Doomworld]], as well as loads of [[FanSequel custom-made]] [[MissionPackSequel megawads]]. In the case of the former, though (possible via Dehacked or by using features of [[GameMod a certain few sourceports]]), it is possible to create [[PaletteSwap recolored enemies]], [[UndergroundMonkey completely different versions]] ([[GoddamnedBats In most cases, either more annoying]] or [[DemonicSpiders far more lethal]]) versions of weaker enemies such as the Zombieman. Certain monsters, such as the [[MascotMook Cacodemon]] or any of the [[DegradedBoss UDoom endboss enemies]] have quite a few variants of them, to say the least. However, there are also a handful of ''actual'' original [=DOOM=] monsters out there.
* The ''VideoGame/PhantasyStar'' series (prior to the ''Online'' games, anyway) has the Espers, and the Hunters: Espers are a race of magical, reclusive people with magical abilities who all come from the same Mansion, Hunters are monster-slaying bounty hunters who operate out of a Guild. There's also the Lutz lineage; Rune is the Fifth Generation Lutz, which means there were three others before him, and presumably, whoever comes after him will be Sixth. Pretty much all original characters for the series fall into one of those three camps.
* One of the races in the ''Literature/LandOfOz'' series are the phanfasms, creatures who have human bodies but the heads of various animals. In the flash game ''VideoGame/EmeraldCityConfidential'', one of the characters is revealed to be a double agent for the phanfasms. The main character, Petra, is confused because he looks completely human. He points out that phanfasms have animal heads, and humans are animals, are they not? [[spoiler: He was wrong, he was a human raised by the phanfasms. But he raised an interesting point that's similar to this trope]].
* It's common in some ''VideoGame/ValkyrieProfile'' fan circles to introduce other Valkyries, usually taken directly from Norse Mythology. Brunhilde is particularly popular. This is in spite of the fact that there are canonically only three due to being combined with the Norns and being a very literal FreudianTrio. Despite this, ''VideoGame/ValkyrieProfileSilmeria'' did introduce a possible mechanism for other Valkyries to be introduced, not that it's taken advantage of by fans.
* When it comes to suggestions for ''VideoGame/BloonsTowerDefense'', the most common "new bloon rank" suggestion given is a new MOAB class containing 4 ZOMG bloons. For reference, the ZOMG is the current strongest bloon.
* ''VideoGame/CookieClicker'' has various suggestions fall under this.
** As of April 2014, element related building suggestions are common, despite the fact we have Antimatter Condensers and Prisms. Double if they are described as "condensers", "converters", or any word of the like. However, as of May 2014, they thankfully died out.
** There are many "new best building" ideas on the forums, but it is slightly justified because of the fact it's one of the more obvious suggestions to make.
* An in-game example - in ''Disgaea2CursedMemories'' Rozalin becomes outraged that the Prism Rangers only have five colors represented, not seven, and after beating them demands that they fill the missing positions.
[[/folder]]

[[folder:Visual Novels]]
* This isn't too hard for the ''Franchise/AceAttorney'' series. You just need to think of a PunnyName for your new lawyer/police detective/murder victim/suspect/etc and give them a few personality quirks.
** ''Dual Destinies'' asserts the trend name for lawyers of the Wright Anything Agency: Myth-inspired first name, legal term-inspired surname, a suit color, and if you're going the extra mile, a weird hair shape. For everyone else, a visual motif doesn't hurt.
* In ''VisualNovel/FateStayNight'' by TypeMoon, the First and Second Grail Wars have been COMPLETELY blank for Masters and Servants, as well as only 2 Servants named and 2 more mentioned for the Third Grail War with 0 Masters. Some fan stories have filled in their events, commonly stuffing the first one with purely Japanese spirits. Some even add in new classes based on a few throwaway lines.
** There have been [[Literature/FateStrangeFake Grail]] [[LightNovel/FateApocrypha Wa]][[VideoGame/FateEXTRA rs]] outside of the Fuyuki one, meaning one can set a story in an all-new Grail War. Creating a Servant is quite simple: find a legendary figure and make Noble Phantasms based off the most notable artifacts and events in said legend's life.
* ''VisualNovel/{{Tsukihime}}'' has a sort of most-wanted list of bad guys, the 27 Ancestors of the Dead Apostles. Several of these are still unrevealed, making it easy to introduce a new villain as one of them.
* Similarly to the ''Franchise/AceAttorney'' example above, it's incredibly easy to insert new super high school students into ''VisualNovel/DanganRonpa''. It's as easy as thinking of a talent or profession which ''hasn't'' already appeared in the games, giving it to a new student with a quirky personality, and [[BreadEggsMilkSquick throwing them into a despair-inducing game of mutual killing]] hosted by a [[KillerTeddyBear psychotic stuffed toy]].
[[/folder]]

[[folder:Web Comics]]
* As one might guess from the title, The ''SailorSun'' webcomic makes full use of this trope even though it should not be confused with the trope itself.
* ''[[http://www.sailorranko.com/ Sailor Ranko]]'', another webcomic based on ''Franchise/SailorMoon'' fanfiction, in this case a well-known FukuFic series that uses the Sailor Earth trope to shoehorn ''RanmaOneHalf'' characters into ''Franchise/SailorMoon''.
* Prematurely shot dead by ''WebComic/{{Periodus}}'', after the creator claimed that now someone could make MarySue fic about Oxygen, and a commenter threw out a several-sentence parody.
* ''Webcomic/{{Homestuck}}'' revolves around sessions of a special computer game called Sburb. It's not uncommon for fans to invent their own characters who order and receive the beta in the mail, particularly on the Forum Adventures section of the forums.
** It's implied that the four canonical kids are the only ones left, given that there seem not to be more "exiles" and the kids' meteors are by far the biggest ones (presumably marking them for the only session that actually gets in). It's implied that nobody else who actually received the game actually got into the medium because they [[PlotInducedStupidity couldn't figure out how to get into the Medium]], which is portrayed in canon as a fairly simple process. [[MisaimedFandom This of course is totally ignored by fan-adventure writers.]]
*** It's only [[http://www.mspaintadventures.com/?s=6&p=002776 Dave and Jade's meteors]] that dwarf all the others; [[http://www.mspaintadventures.com/?s=6&p=002774 Rose's twin meteors]] are pretty average-sized, and John's isn't given the same examination but is probably even smaller. The kids' Sburb session breaks a lot of the rules anyways, so having unusually gigantic meteors for half its players could be part of that anomalousness. Also, given that they have the ''entire planet Earth'' to be exiles in, it's not that implausible that the groups of exiles corresponding to the main and the Sailor Earth sessions just haven't crossed paths. (Given how much predestination figures in the plot, it could be quite reasonably {{Hand Wave}}d as the exiles for each session being drawn to each other and only each other.)
*** There's no excuse, however, for the multitude of fan troll sessions - the twelve canon trolls are explicitly the only ones who will ever play Sburb (or rather Sgrub) because their version was coded by a few of their own players, not released by a company like on Earth. The most canon-friendly fan sessions are the ones that invent entirely new species for the players to be, which are in themselves an example of this trope given how similar they tend to be to the trolls - most fan-created species have their own romance system, calendar, family structure, and equivalent of bedding [[FollowTheLeader because the trolls were different in these fields]].
*** Also, why does everyone always forget [[BadassBystander fedoraFreak]]? Text messages on Dad's phone reveal that one of his acquaintances (actually their neighbor) actually entered and survived in another instance of the Medium and presumably reached God Tier, since the last correspondence with him has him dying on a Quest Bed. That certainly provides a whole load of precedent.
** Such a plot was actually used as an AlternateRealityGame-like [[http://members.shaw.ca/aknowlan/forapocalypse2.html explanation]] for upgrading the fandom's [[strike:forums]] [[InsistentTerminology fora]] software.
** A popular subset is making a {{Crossover}} - characters from another work play Sburb while chatting between each other. Sometimes, the author deliberately doesn't reveal what is the crossed-over verse, challenging the reader to guess what it is from the characters' [[OnlineAlias chumhandles]] and conversations.
** Related to this trope, the author [[http://mspandrew.tumblr.com/post/12680094125/answers has joked]] that every fan troll is canon. Even the bad ones.
** Though it overlaps with EpilepticTree, the hypothetical [[http://www.mspaintadventures.com/?s=6&p=006044 (well, formerly hypothetical)]] thirteenth Troll falls into this. Note that the actual thirteenth troll turned out to be an in-universe [[AscendedFanboy Ascended Fangirl]], and is practically an avatar for ''Homestuck'' fandom. In other words...[[StealthPun a fan troll]]. And then she turned out not be a troll, but a new species ... which has its own romance system, family structure and equivalent of bedding. No word on the calendar yet.
** One of the "God-Tier" rewards for the Homestuck adventure game kickstarter was pledging ''ten thousand dollars'' to the game, in order for the person's fantroll to make a cameo appearance (note that the person would have to pay a ''hundred'' thousand for their fantroll to survive beyond the first panel) in-story, which only two people paid for. This, along with the way time and space works in Homestuck essentially have given a proper justification for fantroll or OC kids sessions (they could be thought of as existing within their own universes and timelines, such as the one described in the flashback with the aforementioned cameos).
* A webcomic known as ''Bishoujo Senshi Sailor Earth'' exists, using an already existing character (Naru) as Sailor Earth. However, she was not a part of the original Sailor Senshi team/group of friends and is added based on an answer the creator gave to fans about using Naru as Sailor Earth should she ever be needed.
* Because ''{{Drowtales}}'' has an on-site RP section this is very common, though there are [[http://forums.drowtales.com/viewtopic.php?f=82&t=12195#p494389 very]] [[http://forums.drowtales.com/viewtopic.php?f=82&t=12195#p494391 specific rules]] about how created characters can be related to canon characters, and a few characters have actually shown up [[AscendedFanfic in the main story as cameos]].
[[/folder]]

[[folder:Web Original]]
* ''Machinima/RedVsBlue'': There's fifty Freelancers (one for every (49) American states) and potentially a whole Greek alphabet's worth of AIs, so new Freelancers and AIs are ''extremely'' common.
* ''WebAnimation/{{RWBY}}''. MontyOum has come up with [[https://twitter.com/montyoum/status/406894139746172928 rules on how to name original characters]]:
** The ExtranormalInstitute setting and color-coded characters open a lot of room for Sailor Earths. Just pick a color, give the character an outrageously (and often impractical) looking outfit and you're done.
** The FunWithAcronyms team naming the ExtranormalInstitute practices is used to create entire four-person teams of characters as well and they don't even have to spell out the team name in question (ex. the title itself.)
[[/folder]]

[[folder:Western Animation]]
* ''{{Transformers}}'' makes this even easier, even if you don't take a [[MerchandiseDriven toy that never got to the screen]] or one of the base characters not already in that reboot, and characterise it for yourself. Pick a cool alt for your OriginalCharacter (thanks to Hasbro, even Triple Changers are allowed now) and a name that fits the "CodeName as real name" motif (there's freaking name generators out there), and you're [[StealthPun ready to roll out]]. You don't even need to say ''why'' they're there, because they're there for the same reason everyone else is there - there's a war, dammit! This is okay because Hasbro uses the same method for inventing their own toy-only characters - and their not-toy-only characters. It's one of the few fandoms where the "Sailor Earth" approach is acceptable.
* ''InvaderZim'' is prone to acquiring new Invaders. Or Tallest, if you're feeling ambitious. The creator explicitly mentioned this on the DVDCommentary, saying he would enjoy going to the homes of the little kids who believe they're "Invader Tom" or "Invader Sally" and wrecking their dreams by noting they weren't at the Great Assigning (every Invader, even those that didn't appear, are accounted for). Note that these new Invaders, or any other Irken [=OCs=], almost inevitably wind up going to Earth and ending up in Ms. Bitters' class. Which seems awfully familiar to anyone who watched the "Tak" episode. Also, an alarmingly high portion of these new Irkens have blue eyes - which is explicitly stated to be impossible in-universe.
* The same setup as ''Anime/OjamajoDoremi'' goes for ''TheBackyardigans'', but it's for the purpose of increasing the cast. Also, the Backyardigans have the same theme colors as the five main Ojamajos.
* With Stitch from ''LiloAndStitch'' being Experiment 626, fans have approximately 625 remaining experiments to come up with for themselves. The TV show however, showed some of these experiments and the finale movie listed all 625 of the other experiments in the credits. All that has done was giving your fan-made experiment a name and number unnecessary now.
* ''WesternAnimation/FostersHomeForImaginaryFriends'' FanFic tend to introduce new imaginary Friends moving into the home. However, they're frequently {{Mary Sue}}s. And move into the same room as Bloo. It's even worse when the author decides for some weird reason, that Bloo should fall in love with this Sailor Earth MarySue. Bloo, who never ever showed any affection for female creatures, except for Frankie. That was once, when he saw her in a dress for the first time, and his affection was limited to chanting "She's hot!" all over again.
* Since there are only three official ''PowerpuffGirls'' around, in came a rainstorm of PPG [[OriginalCharacter OC]]s, mostly being Powerpuffs for any other color besides pink, blue and green. When it's not the rest of the rainbow, it's just a new-and-improved Bunny brought BackFromTheDead and beautified, or sometimes it's the introduction of new Rowdyruff Boys (usually in stories where the original ones had a HeelFaceTurn). One of the most well-known Powerpuff Sailor Earths around is Bell, the white Powerpuff from the ''PowerpuffGirlsDoujinshi'' by Bleedman. Even then, she's an antagonist.
* The [[LoadsAndLoadsOfCharacters sheer amount of characters]] in the later seasons of ''JusticeLeagueUnlimited'' make it easy for anyone and everyone to enter their [[OriginalCharacter OC]] into the League with absolutely no disruption of canon at all, except for the distortions that [[MarySue Sues]] and [[GaryStu Stus]] cause if their new characters happen to be them.
* Shoehorning new Lyoko Warriors into the group in ''CodeLyoko'' fic is all too common, as they are in a whole school full of potential new warriors, and they have endless need for new help. And heck, if your character is a girl, she's the [[RelationshipSue perfect thing]] to fill in Odd's empty love interest slot. The only problem with that is, the one time in canon that the Lyoko Warriors tried to bring a new teammate on board, [[SixthRangerTraitor it didn't work out too well for them]].
* ''WesternAnimation/TeenTitans'' fandom contains PLENTY of fics where a new girl or boy (far more rare) shows up in Jump City with uberspeshul powers and a [[DarkAndTroubledPast tragic past]], and joins up as the [[SixthRanger sixth Titan]]. This character is often a CopyCatSue of Raven or Terra. And most are set well after Season 2, where [[SixthRangerTraitor Terra]] did it and sold them out to Slade, making it ridiculous for them to just add one on quickly out of nowhere. The BEST they'd get is honorary status (a communicator and an offer of occasional help in an emergency), keeping them out of the tower to prevent another Terra from sabotaging them from within.
** Plenty of these new Titans seem to indeed be Terra clones, in that they're either working for or related directly to Slade. {{OC}} apprentices were dime a dozen for quite a while.
** The series ends on a very open-ended note, leaving that opportunity wide to the masses to make something of the sort.
** Another popular route to take when creating Teen Titans [=OCs=] is to make a Titans North or Titans South (or a Titans Whatever-country-or-continent-suits-the-story's-purposes), using Titans East as both justification and inspiration. This way, an entire team of new characters can be made without interfering with canon too much. Yet another option is to add a [[SixthRanger sixth Titan]] to Titans East (some might not even consider them a "sixth" member, claiming that Mas and Menos count as one Titan) to pair them off with Speedy or Aqualad. And of course, it's perfectly reasonable and very popular to simply create new [=OCs=] that are Honorary Titans, residing wherever they want and tied down only to a duo at most. And that's just when it comes to creating heroes. Villains and neutral characters are popular among creators too; after all, what fun is a new hero without a new archenemy to wipe the floor with? So in all honesty, Teen Titans is among the easiest fandoms to create characters for, no matter how the creator decides to pull it off.
* ''WesternAnimation/AvatarTheLastAirbender'' finishes on something of a cliffer. Though this was expanded upon later in the SequelSeries ''WesternAnimation/TheLegendOfKorra'', there are many fics that attempt to write a ''Book 4: Air'' (which would make sense, considering how much the show focused on the four elements), creating a number of [[CopyCatSue copy cats]] of any number of characters, be they of the water tribe, Toph's family, relatives of Fire Nation elite, or, obviously, Air Nomads.
** There are tales about a ''previous'' Avatar: Pretty easy to do, since we don't know how may Avatars there have been and we only know the names of six of them (Aang, Korra and the four Avatars immediately preceding Aang: Roku, Kyoshi, Kuruk and Yangchen).
** Another variation is a story about the complete learning cycle of a later Avatar, anywhere from directly after Aang or Korra to an Avatar in a modernized setting. Very rarely it inverts the concepts and has an Avatar living in a futuristic space age.
* ''WesternAnimation/{{Recess}}'' always has the possibility for "The New Kid", or any other of the nameless kids (or their nicknames) present on the playground. It wouldn't be that hard for something like "The Slide Climbing kid" or "The Video Game Kid".
* ''WesternAnimation/WinxClub'' allows the creation of infinite Sailor Earths, as each planet of the Magic Dimension can have as many Guardian Fairies as needed, not counting the [[DarkMagicalGirl Witches]] nor the [[KnightInShiningArmor Specialists]]. And even when the show has its own share of fanfics, its visual and fashion-centered approach prompts the fandom to create new fairies with their own [[http://janekim.deviantart.com/art/Jane-Kim-Enchantix-92522705 outfits]] and their [[http://www.youtube.com/watch?v=lh9yI57pqSY&feature=related own]] [[http://www.youtube.com/watch?v=FZBttzyyEG0 transformations]]. And yes, there is such a thing as [[http://waliafairy.piczo.com/?cr=3 Sailor Enchantix]] and [[http://novascorpion.deviantart.com/art/Enchantix-Moon-68652046 Enchantix Moon]].
* Every version of ''WesternAnimation/StrawberryShortcake'' also allows the creation of infinite Sailor Earths. The characters are named for food. Limitless, eh?
* It's not hard to have [=OCs=] for ''WesternAnimation/CodenameKidsNextDoor''. Just pick a number.
** Or become a member of the Safety Patrol. Or be delightfullized. Be CrazyAwesome as a child or teenage character. Make some sort of villain (just come up with a concept you dreaded as a kid).
* The ''WesternAnimation/TotalDrama'' series, by virtue of having its contestants based on teen and elimination game stereotypes, is particularly suited to such knockoffs:
** Remakes of the first season often have one or two new characters join the canon cast. If there is only one, it will usually be an AuthorAvatar.
** Stories set in new seasons tend to use ostensibly original characters that have [[SuspiciouslySimilarSubstitute remarkably similar characteristics]] to the canon cast. This is easily--sometimes explicitly--justified with the conceit that the in-universe producers are screening for certain types, and [[TropesAreTools has the benefit]] of freeing the writer from having to acknowledge canon relationships, for example.
** More audacious fics such as ''[[Fanfic/TotalDramaComebackSeries Total Drama Battlegrounds]]'' may introduce a whole new cast of stereotypes while keeping the original cast as well.
* Fans tend to create their own [[WesternAnimation/{{Nine}} stitchpunks]] with numbers of 10 and higher. Which may or may not totally defeat their original purpose, or maybe the fans just imagine themselves to be the scientist's partners who all decided to band together and create an army of stitchpunks for a more likely chance of destroying the machine, or... whatever, my brain hurts.
** Another common practice is creating a stitchpunk named 0, who is almost always a prototype created by the scientist or an elder stitchpunk created alongside 1 and 2.
* ''WesternAnimation/XiaolinShowdown'' gets this a lot too, though the fanfics seem to be split evenly between making a new kid show up, or making Jack a Xiaolin monk as well. As with the ''Anime/DigimonFrontier'' example above, this always involves making a "new element". The most common choices are metal, plants/flowers, and on occasion, [[WhatKindOfLamePowerIsHeartAnyway Heart.]]
* Many ''WesternAnimation/RoadRovers'' fans loved creating their own, by simply picking a breed, gender, nationality, and maybe superpower.
* Another fandom that makes this easy is the ''WesternAnimation/StormHawks'' fandom. All you need is to either pick a pre-existing species (Merbs are the most common in fanfiction) and pick the name of a bird. Most of these also tend to be a love interest for Stork, of all people...
* ''{{Tugs}}'' revolves around two fleets of tugs. To introduce a new character, all that's needed is for one of the fleet's captains to suggest that they need another tug because there's too much work, or (in the case of the Z-Stacks) to make them more evenly matched against the Star Tugs. The series also suggests there are lots of other tugs, and there are plenty of locations in and around the port that we haven't seen yet. And then there's the many background characters that were never developed during the series run.
* Considering the masses of characters in the WesternAnimation/LegionOfSuperheroes, slipping in a hitherto-unseen OC who recently got transferred to the main team (aka, the relevant team) is easily done.
* Because of how common it is for ''XMenEvolution'' fans to create Original Characters, some people have advertised stories where the basic premise is 'Create your own OC for my new OC group of Students'. It's a review gold mine on FanfictionDotNet.
* Similar to ''{{Transformers}},'' you can always bring in your favorite comics X-Man, Legionnaire, or other who wasn't in the show. Some of these take on PossessionSue status.
* ''MyLittlePony'' has LoadsAndLoadsOfCharacters in pretty much all its incarnations, and there's a ''ton'' of "OC Pony" fan-art out there. ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' has inspired fanfic not only about the "Seventh Element of Harmony", but {{Evil Counterpart}}s to the Elements (Generosity vs. Selfishness/Greed/Avarice, Laughter vs. Despair, etc.), usually known collectively as the Elements of Discord. Note a bogus Season 2 episode list that got widely circulated and believed included an episode about the Seventh Element of Harmony.
** Trixie making a HeelFaceTurn and becoming the Seventh Element is quite common.
** Fan favorite Derpy Hooves is often depicted as hanging out with and interacting with the Mane 6. Her fanon-established daughter Dinky is similarily often included with the Cutie Mark Crusaders (despite having been repeatedly depicted with a cutie mark, although it keeps changing).
** Besides, as it is a world inhabited by what's deemed to be MANY Ponies, one simply needs a name and a cutie mark… you would not be hard pressed to find a brony with a Pony OC.
** Probably no other element rings as many Sue alarms as {{Winged Unicorn}} original characters. Only four of those have ever been seen in the show as of season 4 (Five if you count Changeling Queen Chrysalis, who is technically not a pony, but has a horse-like shape, wings ([[GoodWingsEvilWings albeit insect ones]]) and a horn), all of them [[EverythingsBetterWithPrincesses royalty]] and two of them [[PhysicalGod control celestial bodies]], no less. Needless to say, due to SpecialSnowflakeSyndrome winged unicorns tend to pop up a lot in fanfics, and if your fanfic has a winged unicorn OC, you had better have a ''very'' good plot reason for it to exist, because it's most likely something akin to a god.
* This is really common with the [[DisneyPrincess Disney Princesses]]. All you need to do to make an [=OC=] Disney Princess is to give her a fairy tale-esque story and designate her to a specific culture. Many [=OCs=] have been made on the premise of adding an Indian princess, a Spanish princess, a Pakistani princess, etc.
** There's also the fact that the princess line is based off of real-life folklore and fairy tales (albeit, more loosely in some cases than others), so there's the added fun of taking a fairy tale not yet done and adding some {{Disneyfication}} to them. One notable (and very well-done) example would be the fanfiction ''FanFic/HopeSpringsEternal'', which basically converts the Persephone/Hades love myth to the movie-verse and naturally includes a Disney version of Persephone, of the author's creation.
* Comes up from time to time in ''WesternAnimation/ThunderCats'' fanfiction, both for the OS and the [[WesternAnimation/ThunderCats2011 reboot]]. There are many cat species not used in the show for writers to choose from. Add in how the reboot expanded on the species of the other animal races, and there are even more possibilities.
* ''WesternAnimation/AdventureTime'' has a large cast of [Noun] [Royalty]s, especially [[EverythingsBetterWithPrincesses princesses]], so it's not that hard to invent a new one. Oddly, the most popular kind of OC seems to be an Ice Prince(ss), who is generally either the child or niece/nephew of [[AnIcePerson the Ice King]] (which makes little sense given what we know about him in canon). Long-lost relatives of [[EmperorScientist Princess Bubblegum]] and other humans (sometimes serving as love interests for Finn to fill the void left following his break-up with Flame Princess) are also fairly common.
* With the release of ''Disney/WreckItRalph'', plenty of fans have come up with their own ''Sugar Rush'' Racers. All you need to do is make a boy or girl that wears a dessert, confectionery creation or any sort of sweet food themed clothing, and then give him or her a ridiculous name. A bit like ''StrawberryShortcake'' but with a CoolCar.
* ''WesternAnimation/{{WITCH}}'' being similar to ''Franchise/SailorMoon'' (five girls chosen to be [[MagicalGirlWarrior Magical Girl Warriors]] as part of an ancient tradition) gives plenty of fodder for entire teams of original characters with [[FunWithAcronyms team names made of the first initials of the characters]] in fanfics and fanart. There is even a fan-created electronic paper doll makers so users can create a Guardian [[http://hapuriainen.deviantart.com/art/W-i-t-c-h-guardian-maker-167755079 here]].
* No doubt some ''WesternAnimation/ThreeTwoOnePenguins'' fan will add an original female character to the main cast.
* The abundance of British locomotive types has made making original characters for ThomasTheTankEngine extremely easy. Road vehicles, boats, planes, humans, even non-British locomotives are also no-brainers, to the point that foreign locomotives like Hank, Bash, Dash and Ferdinand (USA), Flora (Ireland), Hiro (Japan), and Millie (France) are canon.
* ''WesternAnimation/StevenUniverse'' already seems to have gotten this early in the show's life, with the occasional story about a new Crystal Gem being involved in one way or another. Even though it's been implied by the series's first promotionals that the four we see on the show are the [[LastOfHisKind last Crystal Gems on Earth.]]
* There are an insane amount of ''WesternAnimation/SouthPark'' fanfics that involve a new kid (usually female) moving to town and becoming friends with the four main boys. If the character is a girl, as is the case with 99% of these stories, a romantic relationship is pretty much guaranteed, with Kyle being the most popular boy to pair her with.
* One can pull this trope off in EverAfterHigh and its Spiritual Predecessor MonsterHigh by coming up with a fairy tale character or monster not already existing in canon and adding them to the main cast/giving them their own adventures within the school.
[[/folder]]

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->And by the way, if there ''were'' a Sailor Earth, it would be Tuxedo Mask.

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