->'''Creator/JohnnyYongBosch:''' Maybe kids will write some fanfics about it.\\
'''[[WebVideo/AtopTheFourthWall Linkara]]:''' We can only hope.

Many times a creative work will leave large gaps in a character's {{backstory}}, or not mention what happened between two instances of seeing a character, or object or place. We might get a bit of explanation, usually a throwaway line that suggests a NoodleIncident, but either way we are left to imagine it ourselves.

So, someone else will, of course, do it for us. Many {{fanfic}}s that don't involve {{shipping}} will fill in any gaps, often with wild adventures [[BigLippedAlligatorMoment that one would expect would get more of a mention in the work if they'd happened, but don't]]. Anything in a work of fiction that leaves inviting gaps can be seen as fanfic fuel. The more outrageous or open for interesting plot developments, the better.

Summers between school years in high school dramas are often great sources of Fanfic Fuel, as well as the draw of giving a mysterious character more backstory (which may result in DracoInLeatherPants) or rewriting things from the perspective of someone else whose viewpoint we never saw in canon.

See CanonFodder, a subtrope.

----
!!Examples

[[foldercontrol]]

[[folder:General]]
* Many of the "could-have-beens" on the WhatCouldHaveBeen page are prime fanfic fuel. The same goes for the ideas on the WildMassGuessing pages.
** Similarly, many one-shot comics and manga (as well as TV pilots) can be used as plots for fanfiction.
* AndTheAdventureContinues invites possible sequels.
* Any work with a TimeSkip that doesn't cover the intervening period in enough detail.
* Putting two characters in a cave or similar small space together will result in a few hundred fics about them [[{{Lemon}} getting it on]].
* SequelNonEntity characters are practically engraved invitations. ''Something'' must have happened to them to prevent their appearance in the sequel.
* Characters [[TheyWastedAPerfectlyGoodCharacter whose potential is never truly unlocked by the canon writers]] will often be taken up by the fanfic writers instead.
* The {{Backstory}} of a character is a good source of this.
* A NoodleIncident is something from the past that is sometimes referred to but never properly explained, with the implication that whatever the truth is, it's far less interesting than anything the audience can imagine. Naturally, any improperly explained incident is just begging for a fic or two dedicated to it.
* Series that end abruptly or unsatisfactorily, as Henry Jenkins cites in ''TextualPoachersTelevisionFansAndParticipatoryCulture'':
--> ''Series/AlienNation'' ended on a cliff-hanger; GeorgeLucas completed only one of a promised three ''StarWars'' trilogies [[note]] This was obviously written before the prequel trilogy was released and the sequel trilogy was announced[[/note]]; ''Series/BeautyAndTheBeast'' denied fans the resolution of the Vincent-Catherine romance; ''{{Blakes 7}}'s fourth season concluded the series with the apparent deaths of its major characters.
[[/folder]]

[[folder:Anime and Manga]]
* ''InfiniteStratos''. For average viewer, it's just a mediocre UnwantedHarem [[RecycledInSpace WITH]] [[InstantAwesomeJustAddMecha MECHA]]. [[VocalMinority Fan Fic writers on the other hand]]... War, politic, social shift... the potential is limitless, and three point above is rarely addressed in the canon source (except small clues here and there) despite it was said the introduction of titular PoweredArmor [[InformedAbility more than few things changed]], leaving the gap for the fic writers to explore. It was not rare to find the sheer difference of atmosphere in I.S. fanfic as the result, from RomanticComedy / {{Shipping}} to GrimDark WarFic, despite the [[SugarWiki/NeedsMoreLove tiny size of the fanbase]].
* ''Manga/DeathNote'' has lots of rules that don't come up in the main plot. Example: if someone's name is written in two Death Notes within a split second of each other, it is regarded as simultaneous and the victim ''lives'', unaffected by either note.
** BackStory: L's / Mello's / Near's / B's / Matt's [[DarkAndTroubledPast Dark And Troubled]] MysteriousPast. What does Wammy's House do and why was it built? / Light's career as a [[KidHero teen detective]] and/or [[ForWantOfANail what would happen if Light didn't find the notebook]] or [[WhatIf what would happen if]] [[spoiler: Light didn't get his memories back.]]
* ''Franchise/DragonBall'' has lots of these. Like the five years between ''Manga/DragonBall'' and ''Anime/DragonBallZ'', the time between the Cell and Majin Buu arcs, the years that Goku spent training with Kami-sama, the years of training before the attack of the Androids 19 and 20... there are many others like those. Also, there is the fact that we know there were at least 20 androids created by Dr. Gero, but we don't know all of them; the fact that Saiyans were sent to other planets when they were babies to grow up with the planet's civilization to later destroy them and come back to Planet Vegeta, that let open the idea that there may be other Saiyans still alive, living in the planets they were assigned to destroy; the alternative Universe Future!Trunks came from, and the idea that more alternative dimensions can be created with the Time Machine... ''Dragon Ball'' is totally made out of fanfic fuel. But it was to be expected from a story of such length (and that was mostly improvised by Toriyama!) and for all the PlotHoles created by the anime series that needed to keep adding fillers while waiting for [[OvertookTheManga the manga to catch up.]]
** It doesn't help either that almost all the movies could be considered {{Alternate Universe}}s because they don't fit very well with the main continuity, so you have many possible universes to tell stories about.
* ''Anime/CowboyBebop'' persistently reveals a lot of background detail to the audience without actually telling them ''anything'', leaving enormous room for speculation. Most of this concerns the past relationship between Spike, Julia and Vicious, though other characters (especially Ein, Wen, and Mad Pierott) aren't exactly lacking.
* ''AxisPowersHetalia'':
** Fans have plenty of fun writing for the nations, with all the history between them.
** The vast amounts of ShipTease and HoYay between nations (in part due to the main cast being [[CastFullOfPrettyBoys almost entirely male]] and AmbiguouslyBi) has lead to many works putting popular (and in some cases [[CrackPairing not-so-popular]]) pairings together, either as Nations, or in a human (usually high-school) AU. The fact most of them has at least one human name suggested by WordOfGod helps the latter significantly.
** The nature of being a Nation is touched on briefly in the series, but much is left up for speculation - like what exactly leads to a Nation's 'disappearance', how emotionally damaging is it to be immortal and how being forced to comply with their bosses' wishes (as is implied with WWII-Germany) affects them.
* The ''Manga/{{Naruto}}'' fandom already were fond of writing AlternateUniverse fanfiction set in high school but when the anime released an ending theme that pretty much set up the roles of each character for them the amount of fanfiction (and fanart for that matter) exploded.
** And then, thanks to Road To Ninja and the [[spoiler:possibility for a LotusEaterMachine Jutsu]], these Alternate Universes have more weight to them.
* ''Franchise/SailorMoon'' spans millenia and follows only a dozen or so girls of what could be hundreds. Naoko did say that there could be senshi all over the universe, and we even meet a couple dozen alien senshi in the last arc/season. Therefore, there's ''reams'' of Silver Millennium, Crystal Tokyo, and "Team Other Than The Sol Senshi" stories out there, and the pile grows all the time. Basically, for any celestial body, there's a Sailor for that.
** There's also Jadeite's [[Anime/SailorMoon anime]] fate. When Beryl pulled a YouHaveFailedMe, she sentenced him to [[spoiler: "Eternal Sleep." No, that's not a dub edit.]] Such a thing seems to ''scream'' "dramatic return someday down the line," especially as it turns out that people in this series [[spoiler: can actually die, so no death stand-in or euphemism is needed if he was truly intended to be dead]]. So the series has a 200-episode (plus an OVA or two) run and ends with no such dramatic return, well, it kinda seemed like an oversight, and fans have been correcting it ever since. He's not even that remarkable a villain and doesn't get much in the way of CharacterDevelopment; it just feels so ''wrong'' when ChekhovsGun doesn't get fired. - the [[Manga/SailorMoon manga]] Jadeite is pretty definitely dead.
** How about Mimete's fate? The last we see of her, she's [[spoiler:trapped in a computer when Tellu pulls the plug]], so unless it's stated otherwise, [[spoiler:all someone would have to do to get her back would be to turn the computer on again]].
* ''Anime/{{Pokemon}}'': Three words: Ash Ketchum's [[DisappearedDad father]].
** The revelation that Ash's new travelling companion, Serena, is ChildhoodFriends with him. Certainly opens up new possibilities/insights into Ash's childhood, and that's before considering the shipping factor (a discussion thread for the pairing was already into triple digits after only ''seven'' episodes).
* ''LightNovel/ZeroNoTsukaima'' starts with Louise summoning a familiar, and accidentally summoning a human from another world. ''Every single fanfic'' starts by simply changing who she summoned, usually as a {{Crossover}} with another 'verse. It's notable enough that our fanfic sub-forum on this very wiki has a thread dedicated solely to collecting interesting Zero crossovers.
** Even when the summon doesn't actually change, the entire ZnT universe is fuel. A Low Middle Ages/Early Renaissance set, with magic and elves? The possibilities are endless (specially when the writers do their history homework)
* ''Anime/AngelBeats'', just Angel Beats. Let's see here...
** TheyWastedAPerfectlyGoodCharacter? How about an entire battlefront of characters? Literally, there were only [[spoiler:six characters]] with an actual {{backstory}} in the anime alone!
** ExecutiveMeddling: Because of this, [[Main/KeyVisualArts Jun Maeda's]] original plan of 26 episodes were cut in half to 13!
** Let's not forget about how the Afterlife Battlefront came to be before Otonashi arrived. From the manga revealing how Yuri & Hinata started the battlefront to the first episode, this gap right here is ripe for fanfic writers to fill in!
** And then there's the ship teasing...
* ''Anime/StrikeWitches'', there exist plenty of non-eroge doujins about the many Witches from around its world. This is set as an alternate timeline of World War II, and the anime only covered a small portion of its European nations. Just think about all the potential there is for fan fic writers and doujinji artists.
* ''Manga/TsubasaReservoirChronicle''. [[spoiler: [[AndTheAdventureContinues Non-ending?]]]]. Check. Not resolving any ships at all? Check. Mysterious characters? Check. Tsubasa is made of this trope, now, if only [[YaoiFangirls the fan fiction writers]] [[AlternateUniverseFic would use it.....]]
* In ''Anime/YuGiOhGX'', Daichi Misawa has six different decks in the first season (not counting a "practice deck" he uses in his entrance exam and the "7th Deck" he uses against Judai) but he only uses two of them over the course of the series, and the themes and strategies of the other four remain mysteries. A ''lot'' of fanfics that feature him explore this further, each author giving opinions on what at least some of them are.
** And on that note: Fire Dragon. The first OP shows him flanked my two monsters: Water Dragon, a dragon made of water that we do see him use, and a similar monster made of fire, that we do not, nicknamed Fire Dragon by fans. Some take is later monster Carbogeddon to be related to it (since Water Dragon is created from two Hydrogeddons and one Oxygeddon), but it was never elaborated upon.
* The Virtual Nightmare Arc in the original ''Anime/YuGiOh'' was supposed to be a FillerArc, but it introduced a unique [[HouseRules House Rule]] to the game called the Deckmaster system. Despite Kaiba's insistence canon-wise that [[LetUsNeverSpeakOFThisAgain they forget it ever happened]], FanFic writers never seem to get tired of using this house rule and putting unique spins on it. (In fact, the ''VideoGame/YuGiOhTheDuelistsOfTheRoses'' may have been a "legit" example of expanding the Deckmaster system.)
* The ending of ''Anime/DaiGuard'' shows that Heterodynes will never stop coming even after the last one in the series is destroyed. That's several fanfics waiting to happen.
* ''{{Gundam}}'': Even the original ''MobileSuitGundam'' made it clear that what was shown on screen was simply one small part of a large war. The UC timeline spans over two centuries, and then there are the AlternateUniverse series, and that's not even considering fans making their own Gundam AU. There's also less of an aversion to fans making up all-new casts due to the practice of introducing a new lead character for every anime, manga and video game.
* ''Anime/PuellaMagiMadokaMagica'':
** WordOfGod confirms that [[spoiler:Homura]] underwent approximately 100 timeloops before the start of the series, which opens up a lot of potential for alternate timeline fics.
** The sheer [[AmbiguouslyGay ambiguity]] of the relationships between the girls (particularly Kyoko for Sayaka and Homura for Madoka) opens up a whole can of [[FixFic fix-fics]] that [[UnusualEuphemism tramples any ambiguity so far into the ground that its Soul Gem shatters]].
** The nature of the MagicalGirl cycle is this: allowing practically any girl to be a MagicalGirl, abilities that straddle the border between ImaginationBasedSuperpower and NewPowersAsThePlotDemands, the various [[AwfulTruth truths]] that [[ManipulativeBastard Kyubey never mentions]] and the in-universe speculation that hope and despair [[EquivalentExchange must balance out in the end]], culminating in [[spoiler:[[AndThenJohnWasAZombie the transformation into a witch]]]] - the [[TragicHero tragic]] [[OriginalCharacter OCs]] practically write themselves.
* ''{{Higurashi No Naku Koro Ni}}'':
** Similar to the above, the reveal that each arc is in fact a different universe, with [[spoiler:Rika and Hanyuu]] hitting the ResetButton every few weeks opens up a lot of potential - [[CashCowFranchise which even the creators have latched onto.]]
** Post-Kai fan works are also popular, due to potential plot lines left hanging, [[spoiler:like whether Satoshi will ever wake up, what happens to [[VillainousBreakdown Takano after she is]] [[RedemptionEqualsLife rescued by Tomitake]], and what Toyko will do next]].
[[/folder]]

[[folder:Comic Books]]
* The ComicBook/{{X-Men}}, and all related books, went through a canonical "six-month gap" around 2000, where Cyclops was believed dead and Cable joined the team to take his place. All that is known at the end of it was that Psylocke and Phoenix had switched powers, giving the former telekinesis but no telepathy and the latter, the reverse.
** The X-Men universe in general, with it's countless number of mutants, possibilities for other schools, and numerous other ways to have new and interesting characters show up.
* In Earth-3490: CaptainAmerica married [[IronMan Iron]] [[GenderFlip Woman]] and thereby prevented the Civil War. So how did Natasha Stark become Iron Woman? How did this affect team dynamics? [[LemonFic What was the wedding night like]]?
* Any comic book universe with alternate timelines throws the door wide open for any number of AU fics.
* Blood aside, [[spoiler: Rorshach's "death"]] at the end of ComicBook/{{Watchmen}} could easily just be Dr. Manhattan teleporting him elsewhere, usually to [[{{Crossover}} another universe]], one example being FanFic/RorschachInEquestria.
* Practically everything about the universe of ''ComicBook/TheLeagueOfExtraordinaryGentlemen'' is this, simply because of its unique premise. In the ''League'' 'verse, [[AllMythsAreTrue every piece of fiction ever produced is simultaneously true]], the universe's history is based on the history of fiction, and every generation produces its own unique fraternity of heroes to fight evil. So far, only a fraction of the universe's history has been described in detail by Creator/AlanMoore, and only a few of the past Leagues have actually been shown -- which is why fans get such a kick out of filling in the details themselves, and coming up with their own possible Leagues (knowing that ''any'' character is fair game for inclusion).
** See for yourself: [[WMG/TheLeagueOfExtraordinaryGentlemen the series' Wild Mass Guessing page]], which is filled with theories about how various works of fiction connect to each other in the ''League'' universe, is even longer than the main trope page for the series itself.
** Even out of the many background plot points that the series ''has'' directly commented on, there are still a butt-ton of unseen adventures that are only vaguely described through in-universe primary sources. The adventures of Prospero's Men [[note]] [[Theatre/TheTempest Prospero, Ariel, Caliban]], Literature/DonQuixote, Amber St. Clair, [[Literature/ThePilgrimsProgress Christian]] and Robert Owe-Much[[/note]], Gulliver's League [[note]] [[Literature/GulliversTravels Lemuel Gulliver]], Literature/TheScarletPimpernel, Captain Clegg, [[Literature/TheLeatherstockingTales Natty Bumppo]] and Literature/FannyHill[[/note]], the Second Murray Group [[note]] Mina Murray, Allan Quatermain Jr., [[Literature/OrlandoABiography Orlando]], [[Literature/{{Raffles}} A.J. Raffles]] and [[Literature/CarnackiTheGhostFinder Thomas Carnacki]][[/note]], and the clashes between "Les Hommes Mysterieux" [[note]] Literature/ArseneLupin, Jean Robur, Literature/{{Fantomas}}, Monsieur Zenith and the Nyctalope[[/note]] and "Die Zwielichthelden" [[note]] [[Film/{{Metropolis}} Herr Rotwang, Maria]], [[Film/TheCabinetOfDrCaligari Dr. Caligare, Cesare]] and [[Film/DrMabuseTheGambler Dr. Mabuse]][[/note]] that precipitated UsefulNotes/WorldWarI have all been referred to, but never directly shown.
** Not to mention the many adventures of Janni Dakkar (a.k.a. "The Pirate Jenny") and the crew of the ''Nautilus'', or Mina and Allan's many years spent WalkingTheEarth after the breakup of the Second League, of which we only get a few brief glimpses in the series proper. Both periods encompass '''decades''' of vaguely described adventures (Janni's crew apparently battled ''Franchise/{{Godzilla}}'' at one point) that are just waiting to be filled.
* Over the years, ComicBook/{{Batman}} has accumulated a small army of much younger assistants who all have their own unique skills and abilities, but can never seem to get out of the Big Man's shadow. What kind of adventures will they have in the future as adult superheroes, when their mentor's inevitable death and/or retirement forces them to carve out their own identities in the DCU?
* ComicBook/GreenLantern has 3,600 sectors worth of {{badass}} space cops--belonging to as many alien species--with their own adventures that we never get to see in the main comics.
* ''ComicBook/OneHundredBullets'' has roughly 400 years of unexplored American history in a world where [[TheConspiracy a shadowy cabal of merchants secretly founded the United States]]; said 400 years includes the family histories of the 13 houses of the Trust, and plenty of opportunities for exploring past incarnations of the Minutemen. The main timeframe of the series has the ''years'' of bloody mayhem that the seven present-day Minutemen got up to before the doomed Atlantic City job, which are only glimpsed in flashbacks in the series itself.
[[/folder]]

[[folder:Film]]
* Happens a '''''lot''''' with Film/TheDarkKnightSaga fanfics featuring how SelfDemonstrating/TheJoker got those scars of his, simply because he was [[UnreliableNarrator so inconsistent about them]] in the film.
** The third film, ''Film/TheDarkKnightRises'', seems to practically be powered by fanfic fuel. First off, it's the TimeSkip - the film takes place eight years after ''Film/TheDarkKnight'', hence a gap for fanfic writers to have a stab at. Then, there are all the backstories of the characters introduced in the film. Bane's background and how he got excommunicated from the League of Shadows. Wayne Enterprises board member Miranda Tate, how she rose up the ranks and [[spoiler: her relationship with her father, Ra's al Ghul]], and the slightly shippy nature of her relationship with [[spoiler: Bane]]. GCPD Officer John Blake - his growing up in the orphanage, his police training and, once the film ends, [[spoiler: how he takes on the mantle of Batman as a Batman-Robin-Nightwing hybrid]]. And of course, Selina Kyle. Her past, how she met her roommate Jen, her misadventures as a younger girl and [[spoiler: all the little Bat-Cat babies she and Bruce would have, since the film ends with them together.]]
** To say nothing of the fact that everyone in ''Rises'' seems to go out of their way to pretend TheJoker [[ChuckCunninghamSyndrome never even existed]].
** And specifically related to ''Film/BatmanBegins'': the League of Shadows' involvement in world history, in light of Ducard's claim that they were responsible for the Fall of Rome, the Black Plague and the Great London Fire. For that matter, there's [[spoiler: the careers of the men who previously held the title of "Ra's al-Ghul"]].
* An example from ''TransformersDarkOfTheMoon.'' By the third film, TheMasquerade is completely broken, and everyone is aware of the Autobots' existence. The movie doesn't go into much detail about this, but there are many ideas that can inspire a fanfic. One is how the nations of Earth are shown to dislike the Transformers (there's a mentioning of poll results stating that half the world would feel safer if the Autobots left). One must also wonder how other countries feel about the US using Autobots for non-Decepticon related problems (such as destroying illegal nuclear plants in the Middle East). Overall, there's a whole potential to explore how Earth must cope with the knowledge that one of the world's most powerful nations has HumongousMecha on its side, as well as the fact that said support also warrants even more alien attacks.
** There's also the matter of why Mikaela broke up with Sam.
** Before [=DotM=], there was a fairly large number of DayInTheLife-style fics regarding Ironhide and Captain Lennox's family. [[spoiler:Then [[KilledOffForReal Dark of the Moon]] happened...]]
* Due to her status as a SequelNonEntity in ''Film/TronLegacy'' (and material expanding on its canon), Yori has become a recurring element in ''Film/{{Tron}}'' fanfic whether she is the focus or is only mentioned in passing. DependingOnTheWriter she either is in hiding as a rebel against [[spoiler:Clu]]'s dictatorship who survives the events of ''Legacy'', was killed during the initial coup or executed during the rebellion [[spoiler:(usually Clu has "Rinzler" do it in an ''epic'' level KickTheDog)]], was never brought over from the ENCOM servers to begin with, etc.
* ''{{Labyrinth}}'' fanfics speculating on [[Music/DavidBowie Jareth's]] backstory are common, in part because even the AllThereInTheManual material had little to say on the issue. How exactly did a handsome RealityWarper who looks, for all intents and purposes, human wind up as the ruler of a land of UglyCute baby-stealing goblins who turn their captives into more of their kind?
* ''Film/{{Inception}}'':
** The movie's famously ambiguous ending, which [[spoiler: suggests that Cobb may have stayed in the Dreamworld after his big heist]], practically begs for a ContinuationFic.
** The details behind the history of [[AppliedPhlebotinum dream-sharing technology]] are left very vague, beyond a brief mention of it being developed by the military for training simulations. And since the existence of the technology is apparently [[TheMasquerade kept hidden from most people]], it makes one wonder what kind of unsavory stuff the government has used it for in the past.
** Related: how did thieves like Cobb and his crew first get their hands on dream-sharing technology?
** Even if you believe that Cobb retires from crime by the end of the movie, what will other dream-thieves do once word gets out that inception (read: '''undetectable brainwashing''') is possible? What's to stop them from using it on world leaders? What's to stop world leaders from using it on terrorists and political dissidents? If one inception job could stop an industrialist from monopolizing the world's energy supply, how will inception affect the world's political landscape?
* ''Film/WhoFramedRogerRabbit'':
** The history and origins of the {{Toon}} race.
** [[AlternateHistory Toons' effects on world history.]]
** Eddie and Teddy Valiant's careers as {{Private Investigator}}s.
** [[WhatDoesSheSeeInHim How Roger and Jessica met and fell in love.]]
** Judge Doom's origin and StartOfDarkness.
** If Toontown survived into the present day, what does it look like now?
** The ending seems to open up the possibility that certain features of the modern world [[spoiler: (like freeways)]] don't take off in the movie's universe. How will that affect the state of the world?
* ''Film/IndianaJonesAndTheKingdomOfTheCrystalSkull'' establishes that Indy was an active OSS agent throughout the whole of UsefulNotes/WorldWarII, opening up six years' worth of high-stakes adventures fighting the Nazis in the middle of an all-out shooting war (the original trilogy took place in the years just prior to the war). And that's not counting the ten-odd years that he spent spying against the Russians with the CIA between the events of ''Last Crusade'' and ''Crystal Skull''.
** Also: there's the famous ending of the original ''Film/RaidersOfTheLostArk'', which heavily implies that the US government has a secret warehouse of mystical artifacts that [[HeroOfAnotherStory other G-men like Indy]] acquired in previous secret missions. What artifacts are the government hiding? How did they obtain them? What are they planning to do with them?
* ''StarWars'': Long before the prequel trilogy was released, there were fanfics about the rise of the Empire and Anakin Skywalker's turn to the Dark Side.
[[/folder]]

[[folder:Literature]]
* The ''Literature/HarryPotter'' series has LoadsAndLoadsOfCharacters (students, ghosts, professors, shopkeepers) and several summer holidays for those characters to have adventures on. The main trio in ''[[Literature/HarryPotterAndTheDeathlyHallows Deathly Hallows]]'' are away from Hogwarts for much of the year, so that leaves even more gaps to fill.
** Also, the very explicit, but non-detailed events and descriptions mentioned by various characters throughout the series, coupled with very effective characterization set up by the chapter "Snape's Worst Memory" have given rise to a huge quantity of fanfic set in the era of Moony, Wormtail, Padfoot and Prongs, with dozens of different plays on various unseen canon events.
** And there's the short span in which Ron and Hermione are absent from the narrative in ''[[Literature/HarryPotterAndTheDeathlyHallows Deathly Hallows]]'', during which they [[spoiler:get basilisk fangs and destroy a Horcrux. Considering how emotionally traumatizing destroying a Horcrux is, and that they have their first on-screen kiss immediately following this,]] there's an entire sub-genre of fanfic there.
* Two points in the ''[[Literature/TheChroniclesOfNarnia Chronicles of Narnia]]'' have launched a thousand fics:
** 1.) Most of ''Literature/TheLionTheWitchAndTheWardrobe'' covers the first several days the main characters spend in Narnia. Creator/CSLewis devotes approximately two paragraphs in the final chapter to the following years -- or likely, ''decades'' -- they spend in Narnia [[spoiler:before abruptly returning (and de-aging) to England the very day they had left]].
** 2.) Susan's absence in ''Literature/TheLastBattle'' is brought up once, quickly dismissed, and never mentioned again. Adding to [[InferredHolocaust the potency of]] [[NoEndorHolocaust this fuel]] is the [[UnfortunateImplications phrasing of the reason given for her absence]].
* ''Literature/TheHungerGames'' has ElsewhereFic fuel aplenty. After all, ''someone'' (be it a canon character or an OC) has to have won the [[DeadlyGame Games]] for years 1-73, and most of them we know little or nothing about.
* Many times in the Literature/SherlockHolmes canon, Dr. Watson includes references to cases that Holmes has solved but which were not fleshed into stories, such as the the tale of the giant rat of Sumatra (a story "for which the world is not yet ready"). A large percentage of FanFic, including published pastiche novels, centers on one or another of these {{Noodle Incident}}s.
** Also, the stories often end ''immediately'' after the mystery is solved, and any non-mystery fallout of the main plot, such as processing of criminals, recovery from traumatic events, shocking revelations and conflicts caused by a case, healing of injuries, explaining that needs to be done to other characters, etc, are usually dismissed with the implication that it was all taken care of without incident (or at least, without enough incident for Watson to spoil the pacing of his stories by reciting all the details). However, some of the implication of what these glossed-over details involve are quite intriguing -- trials for the captured criminals, ruined families and friendships, swearing of revenge, or intensely emotional scenes between Holmes and Watson (or Holmes' apparent non-reaction to emotional incidents). Therefore, there are gazillions of fics revolving around the aftermath of various canon cases. In particular, there is a whole genre of fic involving Watson mourning Holmes/Holmes as a fugitive after The Final Problem or dealing with the reveal of Holmes not being dead in The Empty House. Holmes' fright about Watson's injury after The Three Garridebs, Watson throwing a fit at Holmes for his manipulation of him in The Dying Detective, and speculation about how Watson weaned Holmes off cocaine, are also common fanfic plots.
* ''Literature/AWrinkleInTime'', in addition to all the science fiction elements not explored in great detail (the history of the [[IndividualityIsIllegal planet]] [[{{Dystopia}} Camazotz]], the [[AnotherDimension 2-dimensional planet]], etc.), there's also the specific story of the project Meg's father was working on (with the tesseract) and what happened to the first man who tried to tesser. He's mentioned ''very'' briefly, when Meg's father is giving Calvin some of the backstory about the project. He left successfully, but they never found out what happened to him (and none of the sequels give any indicator, either).
* ''Literature/JohnCarterOfMars'' has several unresolved plots. The most obvious example is the fact that the last novel, ''Skeleton Men of Jupiter'', has an open ending with the protagonist still stranded on Jupiter. Other examples are the fact that by the end of ''A Fighting Man of Mars'' Ghasta is still ruled by the evil Jed Ghron, the missing flier 'The Dusar' from ''Llana of Gathol'', and of course John Carter's own mysterious past, the question how old he realy is and why he cannot remember any childhood.
* ''Literature/TheExilesViolin'':There is a TimeSkip between Serge adopting Jacquie and his death. It lasts for years and is the time when Jacquie learns how to be a detective. There's so much fuel it could fill a midquel novel.
[[/folder]]

[[folder:Live Action TV]]
* ''{{Smallville}}''
** The summers between the high school years in the early seasons. The dominant one is the (in)famous "red k summer" between season two and three, which involves Clark on red kryptonite, which stripped his inhibitions and turned him into an amoral party animal, while Chloe visited him and tried to get him home. You could probably guess [[CoitusEnsues how half of those fics ended...]]
** Then of course, being the origin story of Superman, there are loads and loads of fics that tells the tale of the Man of Tomorrow (literally) in the Smallville universe.
** And then, there is the pre-series times, which has quite a few {{Noodle Incident}}s mentioned in the show. The first meeting of [[FanPreferredCouple Chloe and Clark]] is also frequently used, although [[spoiler:their FirstKiss was shown in season 8]].
** And in season nine, after [[spoiler:Chloe and Oliver]] are StrangledByTheRedString, [[AbandonShipping abandon shippers]] from other factions filled the empty space where the build-up belong.
* Given that it's a show about TimeTravel, ''Series/DoctorWho'' has ''lots''. Pretty much anything that isn't shown onscreen or in an audiobook/audio drama is game. And sometimes even then.
** [[Recap/DoctorWhoS31E13TheBigBang Rory's more than 1,800 years guarding the Pandorica]] and [[Recap/DoctorWhoS30E17E18TheEndOfTime The Doctor's time with Queen Elizabeth I]] are just the tip of the iceberg.
** [[Recap/DoctorWhoS30E15PlanetOfTheDead Lady Christina de Souza's]] past and future capers, especially now that she has a flying bus, could qualify.
** And of course, any adventures [[Recap/DoctorWhoS30E6TheDoctorsDaughter Jenny]] may go on to have. Case in Point: ''Fanfic/SomeoneYoudAdmire''. Among others.
** Or for that matter, any adventures [[Recap/DoctorWhoS32E7AGoodManGoesToWar Vastra and the other Jenny]] have already had.
** There is the alternate universe that was first visited in series two and where Mickey decided to stay to help the effort against the Cybermen; at the end of the series [[spoiler:Rose is trapped there with her family]] and in series four [[spoiler:Human!Doctor and Rose are living there together; a deleted scene showed that they could eventually grow their own TARDIS, though WordOfGod from Steven Moffat denied this idea of the TARDIS]]. What else could the fanfic writers want?
** Not to mention various fan attempts of fleshing out companions into more rounded and complex characters than presented in the show (Tegan, Nyssa, Peri, Mel, and other underdeveloped companions get this treatment in fan fiction).
** During the Dalek invasion in [[Recap/DoctorWhoS30E12TheStolenEarth "The Stolen Earth"]]/[[Recap/DoctorWhoS30E13JourneysEnd "Journey's End"]], we saw that Sarah Jane, Rose, Jack and Martha helped with the fight. But what about Ian, Barbara, Ben, Polly, Jo, the Brigadier, Tegan and Ace? All of them encountered the Daleks and were presumably still alive and on Earth at the time. Seems hard to believe they would have just been sitting around...
** Then there is the fact that Clara [[spoiler:was scattered through the Doctor's timestream to save him from the Great Intelligence. She could be written into old or new stories.]]
** The two-parter [[Recap/DoctorWhoS32E1TheImpossibleAstronaut "The Impossible Astronaut"]]/[[Recap/DoctorWhoS32E2DayOfTheMoon "Day of the Moon"]] has the three months that [[FiveManBand The Doctor, Amy, Rory, River and Canton Delwaware]] spent [[LaResistance fighting the Silence's secret occupation of America]].
** Rose's time as a Torchwood operative between the events of [[Recap/DoctorWhoS28E13Doomsday "Doomsday"]] and "The Stolen Earth". We know that she worked for the alternate version of Torchwood in [[AlternateUniverse Pete's World]], but the show never gives any details about what she got up to during her time with them.
** The introduction of the Chameleon Arch in Season 3 opens up some great potential for crossovers, since it means that ''any'' character in ''any'' series could potentially be a Time Lord with temporarily implanted fake memories. Suddenly, all those [[WMG/TimeLord Wild Mass Guesses]] don't seem so stupid.
** Though she's certainly a prominent character in-show, the vast majority of River's time-travelling adventures with the Doctor happen offscreen, with many memorable ones only obliquely referenced. Of the thirteen episodes where River plays a central role, in fact, only ''nine'' of them occur at points when they both know each other--leaving plenty of gaps in both of their lives that might actually explain how they grew close enough [[RelationshipUpgrade to consider themselves a married couple]].
* [[JossWhedon The Whedon Verse]] have seen a ''lot'' of these.
* ''Series/BuffyTheVampireSlayer'':
** Wish!Verse: Remember that AlternateUniverse where Buffy never came to Sunnydale? How did Xander get turned? How did Willow? What happened with Darla? How did Angel became a wreck?
** Insert!Dawn-Fic: Everyone in the Cast was given false memories of Buffy's little sister Dawn in the Fifth season. How would any given episode in the first four seasons play out with Dawn there? In universe certain sources RetCon Dawn into the storyline, the AnimatedAdaptation intended to do this and one of the season eight comics has Buffy dream of season one with Dawn.
** Normal!Verse: "Normal Again" told us that the entire show was a hallucination being created by Buffy in an insane asylum. Describe that world. Maybe the {{Big Bad}}s are all just manifestations of her doctors.
** Yet Another Halloween Fic: Also called YAHF for short, these deal with the episode where people wearing cursed Halloween costumes started turning into the things they dressed as. ''Fanfic/HalloweenWorld'' is probably the most famous among the fandom.
*** Hell, Halloween Fics have sprouted a tiny subgenre: Xander gets all the abilities and hardware (including a certain blue AI) of [[Franchise/{{Halo}} Spartan-117]]
** The episode ''Earshot'' has spawned several fics regarding [[CovertPervert Willow's]] comment about...ahem, [[GenderBender her idea]] of the aspect of the demon.
* ''Series/{{Angel}}'':
** Connor!Be-Gone-Fic: Angel DealWithTheDevil-ed his son into a happy family and removed all memories of his son from his crew. How did this affect their recollection of seasons three and four? How did Wesley get that scar? Also obvious fodder for [[ShipsThatPassInTheNight Connor/Dawn]] angst-fics.
* ''Series/{{Firefly}}'': Anything, really.
** How Wash and Zoe fell in love.
** Simon's time studying as a doctor.
** What Book did before he was a shepherd.
** Heck, let's just say everyone's backstory.
** What was the first time Patience shot Mal?
** The War of Independence
** And probably the biggest one post-''{{Film/Serenity}}'': Where does the ship go next after Miranda?
* The alternate universe on ''TheMiddleman''. What happens with Fatboy Industries? Do alt!Middleman and alt!Lacey save the world? And what does aerosolized soup taste like, anyway?
* ''Series/{{NCIS}}'': Season gaps tend to inspire this on NCIS. How did Tony hold the team together after Gibbs quit? How did Gibbs adjust to his temporary team? How did Ziva survive Somalia? Look up "NCIS" and "Somalia" on fanfiction.net, and you get over two hundred results.
* ''Series/ICarly'': Everyone's parents. Out of the 6 parents of the main trio (and Spencer, who is Carly's brother), only 1 was shown (Freddie's mom Mrs. Benson), 1 was [[NoodleIncident referred to]] (Sam's mom) until she showed up in a single episode, Spencer and Carly's dad is in the military and rarely shows up in one-sided phone conversations. This leaves Sam's father, Freddie's father and Carly/Spencer's mother, and they have never even been mentioned.
** Why did Freddie end up in Seattle, or more accurately, why did his mother come to Seattle on her own, with him. Often combined with the father question.
* Similar with the parents of characters from sister show ''{{Victorious}}''. Only Tori and Trina's parents are seen regularly, Jade's dad was mentioned on one occasion, and both Beck's parent's appeared off screen in on episode. Often fics that mention the parents will have Andre's parents dead, Jade's parents either abusive (especially if it's an angsty fic) or just neglectful and uncaring, the latter being more supported by canon. Cat's parents are generally pretty neglectful as well, though just ''how'' neglectful they are depends on the fic. Robbie, being the ChewToy and TheWoobie will almost never, ''ever'', have a happy home life, and as of "Locked Up'' that view is pretty supported by canon. Beck's usually the only one who will have anything close to good parents, although there will usually be a few issues considering that he lives in an RV just so he can get away from them.
* It's easy to wonder about all the possibilities for adventure surrounding the concept of the Red Pirates in ''Series/KaizokuSentaiGokaiger'', as they traveled the universe gathering the Ranger Keys.
* ''Series/{{Supernatural}}'' gives fans Dean and Sam's entire childhood to deal, Sam's "Stanford Era" is popular, though it doesn't necessarily focus on Sam. The rest of their childhood leaves plenty of questions. Just how much ParentalNeglect did the boys actually suffer? How many schools did they go to? What caused the rift between Bobby and John? The list goes on.
** There are also the multiple [[AlternateRealityEpisode alternate realities]] established/suggested: "What Is and What Should Never Be" (2x20), [[ItsAWonderfulPlot "It's A Terrible Life"]] (4x17), [[BadFuture "The End"]] (5x04), and [[AlternateHistory "My Heart Will Go On"]] (6x17).
** Also, the four months Dean was in hell (or the 40 years, depending on the brother the fic focuses on)
** The season finales have a tendency to leave a few questions unanswered, which has authors try to explain what will happen before the next season premieres. There are also frequent {{time skip}}s between seasons, which work for this.
* ''Series/{{Bones}}'': the post-Season 5 hiatus(during which time Booth and the Jeffersonian team went their separate ways for nearly a year) has produced quite a few fics. Many of them are also Fix Fics, designed to get Booth and Brennan together, usually [[DieForOurShip eliminating Hannah Burley in the process]].
** The fact that we didn't actually see Booth and Brennan [[TheyDo finally resolve their]] UnresolvedSexualTension in "The Hole in the Heart" has been fodder for more than a few fics. One notable(and lengthy, at nearly 200 chapters and still going) fic, "[[http://www.fanfiction.net/s/7177882/1/The_When_and_the_How_bA_b_bBone_b_to_bPick_b The When And The How: A Bone to Pick]]", suggests that they didn't actually do the deed while she was staying at his apartment after Broadsky killed Vincent, but sometime a few days later, prior to "The Change in the Game", after dealing with Vincent's death and getting some perspective on what they really mean to each other.
* A surprising number of ''LoisAndClark'' fics were inspired by the episode "That Old Gang of Mine", specifically one scene where Clark is shot at point blank range by a mobster's bullet. More than a few stories tried to explain how Superman dealt with the possibility that he might never become Clark Kent again, since the rest of the world thought Clark had been killed.
* The ''Series/StargateSG1'' Season 1 episode 'Tin Man' is probably this. After all, the episode ended with android versions of Jack O'Neill and Samantha Carter (plus the others...) roaming around. And the boys didn't realise that they weren't fully human until Doc Fraiser tried to take a blood sample... So everything must be there. I shudder to think of how many fanfics out there have them realising that the military regulations that keep the real Jack and Sam apart no longer apply to the android versions...
* ''Series/BreakingBad'':
** How Gustavo Fring built his meth empire, and the beginnings of his vendetta against the Salamanca Cartel.
** Mike Ehrmentraut's time as a cop before he became a PI and got involved with Gus.
** How Saul Goodman went crooked and built his network of underworld contacts. The producers apparently thought so too, since they decided to greenlight a {{prequel}} spinoff centered on Saul.
** How the OneSceneWonder [[CorruptCorporateExecutive Peter]] [[TheManBehindTheMan Schuler]] got Madrigal Electromotive involved in the meth trade, and how the alliance between Madrigal and Gus' empire started.
** Post-finale:
*** [[spoiler: Jesse's post-Heisenberg life. How will he cope with the resulting psychological trauma from his year in the Aryans' captivity? Will he ever put his life back in order and make an honest living?]]
*** [[spoiler: With "Heisenberg" now one of the most infamous drug lords in American history, what kind of life will his surviving children have? How will Holly White (last seen as an infant) grow up?]]
*** [[spoiler: Did Huell ever leave the safehouse?]]
* ''Series/TheXFiles'':
** By its nature of not showing much of Mulder and Scully's personal lives on screen, the show generates quite a bit of fuel. There are many, many fics about just how Mulder and Scully got from the end scene of "all things" to the opening shot of the same episode; it's heavily implied they slept together, but doesn't show anything else.
** Just what Mulder and Scully did between the end of the series and the second movie (''Film/TheXFilesIWantToBelieve'') is also explored quite a bit in fanfiction.
** The fate of Scully's son William whom she put up for adoption. Many, many fans disliked it and thought his adoptive parents could not protect him from the conspiracy. The fics are about Mulder and Scully searching for him or describing his life.
[[/folder]]

[[folder:Tabletop Games]]
* ''TabletopGame/{{Warhammer 40000}}'', due to the focus on [[CrackIsCheaper selling miniatures]] instead of telling stories and the preponderance of {{Unreliable Narrator}}s provides plenty of space for fan works, with even official material presenting vastly contradictory interpretations of factions, characters and events, the fans following the same policy.
[[/folder]]

[[folder:Theater]]
* In the ''Theatre/{{Wicked}}'' musical, the fact that [[spoiler:Elphaba is alive]] but Glinda is LockedOutOfTheLoop is shipping fuel for {{Fix Fic}}s and {{Dark Fic}}s alike.
** Not to mention the 2 to 5 year (depending on what you like to believe) gap between Act 1 and 2 where we go from Elphaba Defying Gravity to Fiyero and Glinda working for the Wizard and Nessa becoming Governor and enslaving Boq. There's a tonne of missed action just there. Also the fact we only get a few Shiz scenes in the musical...
[[/folder]]

[[folder:Video Games]]
* ''VideoGame/{{Touhou}}''. The lack of backstory for many of the characters or the events of the PC-98 games are prime fanfic (and fan comic and fan video) fuel.
* All of those spartans that didn't get a story on the ''Franchise/{{Halo}}'' games and in the ExpandedUniverse.
* ''SilentHill'', being a premiere MindScrew series told exclusively from the view of the player character ([[spoiler:with the possible exception of ''Shattered Memories'']]), contains a wealth of information for fans to explore, especially concerning the nature of the eponymous GeniusLoci and the cult that worships it.
* Many ''VideoGame/GoldenSun'' fanfics focus on what Isaac's party was up to during the first two thirds of ''The Lost Age'', before they joined forces with Felix's group.
* Several fics based on ''VideoGame/TheLegendOfZeldaTwilightPrincess'' focus on [[spoiler:what happened to Midna after she returned to Twilight, and if she ever found a way to reunite with Link]].
** All the alternate timelines and universes add more of this too. What happened in Termina before and after Link's Adventure in Majora's Mask (and what was Majora's own backstory)? The wars in the past that occurred before Ocarina of Time, A Link to the Past, Skyward Sword and various other titles, of which the BigBad is usually one of the last survivors? What happened to so and so character introduced in one game that's never been heard of since? Each of these questions usually starts a lot of Zelda fan fic...
* ''Franchise/{{Pokemon}}'' has generated massive numbers of fanfics over the years, thanks to the sheer cultural presence in the childhoods of an entire generation. The games (especially the early ones) often had sparse characterization and backstories for many characters (including [[SilentProtagonist the protagonists]]), making [[AlternateCharacterInterpretation alternate character interpretations]] easy for many writers. And we're not even getting into the related media...
* ''VideoGame/MetalGearSolid'' fandom is particularly fond of writing fics about Liquid's backstory (usually set during his time in the Middle East) or the day The Boss killed The Sorrow. In fact, these two plots are so popular in [=MGS=] fan fiction that almost every male [=MGS=] fan writer has taken on the former, and almost every female [=MGS=] fan writer has taken on the latter.
* Very little is explained about Malefor's backstory in TheLegendOfSpyro: Dawn of the Dragon. Any fanfiction that's not Spyro/Cynder shipping is probably this. His "death" in the final game was also vague, leading to many fanfiction and fan comics.
* ''[[VideoGame/SoulSeries Soulcalibur V]]''. Gets barely over a year in development. [[http://train2game-news.co.uk/2012/03/26/train2game-news-soulcalibur-v-story-mode-one-fourth-of-planned-size-each-character-was-to-have-own-story/ The length of story mode is drastically shortened due to time constraints,]] with ''numerous'' plot elements mentioned in official bios prior to the game's release being ignored or glossed over left and right and only a [[NoExportForYou Japanese-only artbook]] attempting to [[AllThereInTheManual fill in the blanks]] of exactly ''what'' happened in [[TimeSkip the seventeen-year interim between]] ''SCIV'' and this game (heck, there aren't even character-specific Arcade endings to help shed light on things). You can bet your soul (pun intended) fanfic writers are scrambling at this very moment to answer the various questions that ''SCV'' couldn't bother to.
* ''VideoGame/TalesOfSymphonia'' has a two-year gap between the first and second games in the series for fanfic writers to speculate on. Most of the party members also have at least a few gaps to fill in...not to mention the oft-mentioned but barely-seen Kharlan War era, four thousand years ago, which has spawned its own subgenre within the fandom.
* Similarly, there's plenty in the post-timeskip epilogue to ''VideoGame/TalesOfTheAbyss'', except that it's more like essay fuel since people are just trying to explain [[GainaxEnding what the hell actually happened.]]
* While the MMO game ''VideoGame/TheMatrixOnline'' might have been disappointingly short-lived, it did manage to open up a very open-ended continuation of the ''Matrix'' film series, where factions of human warriors loyal to Zion, the Machines and the Merovingian wage a secret war for control of the Matrix in the wake of the Machines' truce with humanity. Many fanfic writers have taken to using this setting as a starting point for {{Continuation Fic}}s exploring the future of the ''Matrix'' universe.
* ''Franchise/MassEffect'' fans have the two years in which [[spoiler: Shepard is "dead"]] to explore what happened to their old crew, as we only really find out what happened to Garrus and Liara, and even they don't get much detail.
* ''VideoGame/MegaManZero'': [[spoiler: The BigBad is immortal, and Zero's death is left ambiguous.]] Did something else happen to these two after Zero 4?
* Before Radical Dreamers' and Chrono Cross' release, ''VideoGame/ChronoTrigger'' has many fanfics centering about Magus' search for Schala because Schala's fate is left ambiguous in the end.
* As a sequel to Chrono Trigger, ''VideoGame/ChronoCross'' has a WildMassGuess about [[spoiler: the enigmatic masked magician Guile being Magus searching for Schala (the bonus ending of Chrono Trigger DS implies Guile being an amnesiac Magus)]]. This leads to many (though still not very common) novelizations of Chrono Cross with the said WildMassGuess.
** It's worth noting that Guile himself is a FanficFuel [[spoiler: regardless being Magus or not]], although his fanfics aren't very common.
*** Guile's Japanese name is Alf, which is probably a nod to Janus' cat Alfador. Some fans interpret him as a cat-turned-human.
*** Some fans also prefer having Guile [[spoiler: not being Magus]] by giving him a BackStory which comes from their interpretations. The most common interpretation is Guile being a magician in the past.
*** This is less common, but the interpretations of Guile's comment [[spoiler: (doesn't want the power of darkness because he thinks DarkIsEvil)]] about the Frozen Flame are also prone to be a FanficFuel. This usually comes across as Guile's denial of his identity [[spoiler: as Magus in the past]], but the Frozen Flame is also said to be able to speak not only about the past but also the future.
*** Another less common FanficFuel is about what Guile is hiding behind his DominoMask. Why is the Fortune Teller at Termina shocked when he takes it off?
[[/folder]]

[[folder:Web Animation]]
* ''Machinima/RedVsBlue'''s mysterious Project Freelancer has inspired numerous fan fics based on it, the [[WhatMeasureIsANonHuman questionable experiments]] it performed off-screen, and its various agents that all existed before the series occurred.
[[/folder]]

[[folder:Western Animation]]
* Many have wondered what happened during the time skip between the last episode of the second season of ''WesternAnimation/TheTransformers'' and ''WesternAnimation/TransformersTheMovie.''
** Also, since ''WesternAnimation/TransformersAnimated'' left quite a few questions unanswered, plenty of potential there. Especially with the Allspark Almanac Volume 2 coming out, which will contain unused Season 4 material.
*** The same goes for the ''WesternAnimation/TransformersPrime'' finale movie, ''Predacons Rising'' - namely: Where did [[spoiler: Megatron]] go; did [[spoiler: Starscream]] survive his encounter with the Predacons; and how will Team Prime cope after [[spoiler: Prime's death]]?
* The ShowWithinAShow in ''Disney/{{Bolt}}'' could spawn dozens of fan stories.
* Many people wondered what happened between the timelines of ''JusticeLeagueUnlimited'' and ''WesternAnimation/BatmanBeyond''. Fifty years had passed and many of the Justice Leaguers are gone. They've also wondered about the circumstances which led to Warhawk, son of Hawkgirl and Green Lantern, being conceived and born.
** Not to mention the "Near-Apocalypse of '09".
* ''InvaderZim'' contains a surprising amount of background detail upon which numerous fans can and have elaborated, ranging from an interstellar war to Irken reproduction.
** Especially since the show was canceled just as it was developing a MythArc, and the creators have revealed their basic plans to fans.
* ''WesternAnimation/RoadRovers'' has loads of things for fans to expand on, including the relationship between Parvo and the Groomer, [[SailorEarth adding new Road Rovers or creating their own groups,]] and elaborating on the backstories of the Road Rovers.
* The fate of Ursa in ''WesternAnimation/AvatarTheLastAirbender''. The show left a few other minor plot threads hanging, but that's the one that really got everyone upset, and speculating.
** And, you know, a century-long war, with plenty of rich, undeveloped ground for exciting battles and stuff. And one thousand Avatars in the history of the world, too.
* ''[[WesternAnimation/AdventuresOfTheGalaxyRangers Galaxy Rangers]]''? [[TrainingfromHell Wolf Den]] and the [[SuperSoldier Supertrooper Project]] account for a lot of stories. So do scenarios on how to rescue Eliza from the FateWorseThanDeath.
* Long before there was ever a [[WesternAnimation/LiloAndStitchTheSeries series]] to take up the idea, ''Disney/LiloAndStitch'' writers had 624 blank spaces to fill in with fan characters, a vaugely described laboratory for them to be born in, and a universe for them to explore. They made sure to take advantage of this.
* The fanfiction community for ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' is ''huge''. The show has the tendency to drop things that serve as good starting points for fanfiction.
** Why are Celestia and Luna apparently the only winged unicorns in the series?
** Did anything interesting happen in the thousand years between Nightmare Moon's imprisonment and the pilot?
** Luna's 1-year ChuckCunninghamSyndrome.
** Now we have JustForFun/DaringDo, an AdventurerArchaeologist who is the protagonist of a [[ShowWithinAShow Book Series Within A Show]]; the contents of one of the books have been shown on-screen, we know the title of another, and we know that there are many other books in the series. Cue lots of fan-made "[[CharacterNameAndTheNounPhrase Daring Do and the [x]]]" installments.
*** And the JustForFun/DaringDo trope page, if it counts.
** In "[[Recap/MyLittlePonyFriendshipIsMagicS2E17HeartsAndHoovesDay Hearts and Hooves Day]]", the Cutie Mark Crusaders create a love potion, but they only use a very small amount and leave quite a bit in the pitcher. Cue Shipping Fics involving one pony (or more) accidentally drinking the potion and [[HilarityEnsues hilarity ensuing]].
** The introduction of Tartarus and time travel spells in "[[Recap/MyLittlePonyFriendshipIsMagicS2E20ItsAboutTime It's About Time]]" has given rise to many fanfics
** The [[BaseBreaker questionable actions]] of Shining Armor, The Mane Six, and Celestia that were taken during first part of the second season finale had garnered a bit of fuel, having writers insert bitterness into Twilight [[spoiler:when she alienated everyone she ever loved, even when she was right about her suspicions surrounding the fake Cadance]] and write out stories [[AccusationFic calling out the ponies involved]].
** During the space between seasons 2 and 3, Hasbro released a series of ''Friendship is Magic'' posters... including [[http://pixelkitties.deviantart.com/art/Hi-Resolution-Equestria-Map-318946279 an official map of Equestria]] which featured a number of new locales to tickle the imaginations of fanfic writers.
** Trailers for ''[[Recap/MyLittlePonyFriendshipIsMagicS4E23InspirationManifestation Inspiration Manifestation]]'' showing a green-eyed Rarity with her horn glowing the same color had fans wondering if King Sombra or Queen Chrysalis would be involved (they aren't). Given that all of Rarity's designs involve heavy use of crystals and gemstones and Twilight explicitly refers to the book's powers as [[BlackMagic dark magic]], the episode looks to be implying that the book came from Sombra but backs off before stating it, leaving it open to speculation.
*** Given that the jewels were only a result of Rarity's design style and not part of the spell she used, they were probably a red herring as far as Sombra was concerned,[[hottip:*:Especially since the mechanics and effects of his crystal generation spell was completely different]] but the gradual loss of reason and increase in power was similar to the effects of the Alicorn Amulet.
** ''[[Recap/MyLittlePonyFriendshipIsMagicS4E24EquestriaGames Equestria Games]]'': Who are the delegates from other lands, and what are their kingdoms like? Plus, all the characters on the other teams, and what events the other ponies from Ponyville were participating in, and how the parts of the games that we didn't see (which were most of them) went, and Equestria's relationship with the griffon kingdom that sent a team (assuming it wasn't a griffon-majority territory located in Equestrian boundaries), and how the actual anthems of Ponyville and Cloudsdale go...
** As of ''[[Recap/MyLittlePonyFriendshipIsMagicS4E25TwilightsKingdomPart1 Twilights Kingdom Part 1]]'', on top of fans tying the series back to G1 now more than ever, we have Scorpan, another G1 based character and Tirek's brother who befriended ponykind but left soon after Tirek was imprisoned. This is itself a reference to the ''original'' Scorpan, who also pulled a HeelFaceTurn against Tirek near the end of the G1 pilot. Oh yes, and Discord and Tirek know each other somehow.
*** And Scorpan and Starswirl were friends?
* ''Disney/TheLionKing'' has a lot of this. For starters, the movie {{Leitmotif}}, the never ending Circle of Life, means that you can write sagas of the royal lion family. Then, there are lots of characters that were introduced but not developed in comics or books, like Ni, Tama, Tojo. Also there are many story gaps that fanfic writers love to fill, like the years of Scar's reign, or where the Outlanders from the second movie came from.
* The history between Marceline and [[spoiler: Simon Petrikov]] on ''WesternAnimation/AdventureTime''. What we see of it is [[TearJerker extremely]] [[CrowningMomentOfHeartwarming poignant]], it involves two [[EnsembleDarkhorse fan-favourite]] characters, it hints at the somewhat vague circumstances of [[AtomicHate the]] [[WorldWar3 Mushroom]] [[ApocalypseHow War]] (which is this trope in of itself), and it's only been elaborated on in one or two episodes. Perfect FanficFuel.
** For that matter, the relationship between [[spoiler: Simon and Betty]] seems to get a lot of attention.
* The never-seen biological parents of the title characters on ''WesternAnimation/PhineasAndFerb''. Phineas's mother and Ferb's father are married, [[HappilyAdopted they consider them their parents]], and no mention is ever made of what happened to their biological [[DisappearedDad father]] and [[MissingMom mother]], respectively. This has led to a ''lot'' of fan speculation on the subject.
* RocketPower: in the episode "Welcome to [=OttoWorld=]" the Rocket gang burries a time capsule and wonders if anyone will remember them in the future. The episode ends with a scene in which the time capsule is opened again in the distant future, and we get to see four statues of the protagonists. What did they do to apparently get this famous?
* Thanks to it's untimely end, along with [[WhatCouldHaveBeen the original writer, Steve Marmel's plans]] rejected for [[SeasonalRot the third season that did happen]], many things in WesternAnimation/DannyPhantom are prime targets for Fanfic Fuel. Two particular favorites is Dark Danny's return, which the show promised but never did, and [[OppositeSexClone Danielle "Dani" Phantom]] being introduced to Danny's family, adopting her in the process.
* When the entire Justice League got brainwashed and forced to serve The Light in ''WesternAnimation/YoungJustice'', the large gap between the end of the first season and the time skip, you also have the grand finale.
* ''WesternAnimation/HeyArnold'' was supposed to end with its fabled "Jungle Movie," which would have seen Arnold and Helga admit their true feelings for each other, and would have seen Arnold finding his parents, but the show was cancelled before the movie was ever produced. However, creator Craig Bartlett has revealed bits and pieces of the finale's intended plot, and the fanfic community has responded in kind.
** Ditto for Bartlett's unproduced spinoff ''The Patakis'', about the home life of a teenaged Helga. The pilot script was apparently too dark for Creator/{{Nickelodeon}}, but Bartlett has revealed enough details for the fanfic writers to use.
* The ShowWithinAShow format of ''WesternAnimation/TotalDrama'' has naturally led to a plethora of [[FandomSpecificPlot fan seasons]], often populated entirely by OC's. Not to mention the possibilities for what happens to the canon characters ''after'' the show.
* Tai Lung in ''WesternAnimation/KungFuPanda'' has gotten plenty of fanfics about what happened to his real parents and how he ended up adopted. Po got the same treatment until ''WesternAnimation/KungFuPanda2'' revealed his origins.
* The ''Disney/{{Mulan}}'' sequel did nothing to curb this. In fact, there was enough FanWank generated for several [[BetterThanCanon attempted rewrites]]. The first movie itself contains a TrainingMontage covering countless little interactions, Mulan's family dealing with their only daughter [[InHarmsWay out of sight in the army]], the Huns moving in to [[OffscreenMomentOfAwesome massacre the Chinese Army at that village]], and of course that one line:
--> '''Mulan''': (to Shang) Would you like to stay for dinner?
* ''WesternAnimation/{{Gargoyles}}'' has a ton, in no small part due to [[TooGoodToLast its rather abrupt cancellation]], and [[WhatCouldHaveBeen the creator's future plans for the series (which he has vaguely alluded to over the years)]].
** There was going to be a ''Dark Ages'' prequel spinoff focused on the early days of the Wyvern Clan in Medieval Scotland, when Goliath and Demona were still young lovers fighting under Hudson's guidance. Not to mention a planned ''Gargoyles: 2198'' SequelSeries, with the cast's descendants fighting off an alien invasion (first hinted at in "Sentinel") in the far future. Both concepts practically beg for fanfiction.
** The released notes for ''2198'' confirm (among other tidbits) that Elisa and Natsilane's descendants would eventually have gotten together, that Lexington and Xanatos would eventually have merged corporations, and that a line of robots based on Lexington would eventually have entered production. All dynamite ideas for fanfiction.
** After fans pestered him about it in his "Ask Greg" Q&A forum, Creator/GregWeisman confirmed that he did have plans to work characters from [[Creator/WilliamShakespeare Shakespeare]]'s ''Theatre/TheTempest'' into the ''Gargoyles'' mythos. How would they have figured in the story? How would Weisman have portrayed them? How different would they have been from their literary counterparts?
** After Demona and Macbeth were made immortal by the same magic spell, they canonically lived through over 900 years of human history--barely any of which has actually been seen in canon. What adventures did they get up to while Goliath and his pals were still sleeping in statue-form?
** [[GreatOffscreenWar The interstellar war between the N'Kai and the Space-Spawn]].
** Alexander Xanatos' time studying magic under Puck's tutelage.
** Alex Xanatos taking up the mantle of Fox from his mother (a possible future plot point that was hinted at in "Future Tense").
** Queen Titania's relationship with Halcyon Renard.
** Peter Maza's relationship with the trickster spirit Coyote (the specific nature of which was left rather vague in-show).
** The careers of Canmore's descendants who took up the mantle of [[LegacyCharacter "The Hunter"]] after him.
** [[WordOfGay Lexington]] acknowledging and coming to terms with his homosexuality.
** The lives and adventures of the gargoyles in the Wyvern Clan [[WeHardlyKnewYe who were all killed off in the pilot episode]] [[DeathByOriginStory shortly after being introduced]].
** The history and true purpose of the Illuminati.
** The Redemption Squad's battle with the Illuminati after the cancellation of the ''Gargoyles: Bad Guys'' spinoff.
* ''WesternAnimation/ScoobyDooMysteryIncorporated'': The original Mystery Incorporated team from the 1960s likely spent ''at least'' at much time solving mysteries as the classic crew, but their adventures are only hinted at in vague flashbacks. Exploring their adventures opens up a great opportunity for putting a darker spin on the classic ''Scooby-Doo'' formula.
* Because of [[{{Disney/Tangled}} Rapunzel and Flynn]]'s cameo in ''{{Disney/Frozen}}'', some writers were convinced that both movies share the same universe, opening up some doors for ideas.
* Though the finer details were left intentionally vague, plot points in ''WesternAnimation/ToyStory2'' seem to establish that Woody has "lived" for around [[OlderThanTheyLook fifty years]], leaving a huge gap in his backstory that could explain how a coveted antique toy wound up in Andy's possession (or, for that matter, why Woody doesn't seem to be aware of the fictional character that he's based on).
* ''{{Daria}}'''s BizarroEpisode, "Depth Takes a Holiday," is often relegated to FanonDiscontinuity, but other times fans wonder: if Lawndale actually has an interdimensional portal, couldn't that set up all sorts of sci-fi/fantasy fics, not to mention crossovers?
* ''WesternAnimation/YoungJustice'': Gets this. There have been various fics that depicts what the show would have been like had Season 3 happened and fics that involve the possibly theory that Wally ended up in an alternate dimension and he has to find his way back home. There are also fics that focus on The Team after the events of the season one finale and before the season two time skip.
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