* Various explanations for the inconsistencies of how time travel works between the three ''Franchise/{{Terminator}}'' {{movies}} are fanon. The ''Terminator'' movies (and the [[Series/TerminatorTheSarahConnorChronicles TV show]], for example) never state how it works, just that it does.
* Given that [[WordOfGod George Lucas himself]] has said that the only things he considers "official" ''Star Wars'' are the films and the ''Clone Wars'' cartoons, it could be argued that the entirety of the ''Franchise/StarWarsExpandedUniverse'' is nothing but Fanon. [[BrokenBase Some fans would argue with this point of view]].
** Wookieepedia, the ''Franchise/StarWars'' [[TheWikiRule Wiki]], has a fairly complete [[http://starwars.wikia.com/wiki/List_of_fanon_elements_in_continuity list]] of fanon elements that have found their way into the official continuity, either as an intentional homage or due to the authors mistaking them for canon.
** [[http://supershadow.com/ SuperShadow]] is a website dealing almost exclusively in bizarre fanon notions; its webmaster alleges that he is a close personal friend of George Lucas. Most ''Star Wars'' fans avoid the site, and discussing it in a serious forum [[FandomBerserkButton is a good way to rankle a lot of people]]. PoesLaw is in full effect here; fans can't tell if the guy is serious or just making fun of other fans' bizarre fanon ideas.
** Anakin was prophesied to bring "balance to the Force", but no one is sure what that "balance" is supposed to be. WordOfGod says that he was destined to destroy the Sith (which he does, by [[TakingYouWithMe killing the Emperor and dying himself]] in ''Film/ReturnOfTheJedi''). But many fans believe this prophesy refers to the BalanceBetweenGoodAndEvil -- and in the prequels, Anakin does kill all the Jedi other than Obi-Wan and Yoda, leaving two Jedi and two Sith. Other fans claim that the very existence of the Sith implies imbalance. This has caused endless arguments, with each theory ''plausible'' but rendering various parts of the saga an IdiotPlot. ''Webcomic/DarthsAndDroids'' describes the debate in the blurb of [[http://www.darthsanddroids.net/episodes/0146.html this strip]].
** ''Film/ThePhantomMenace'' introduced the concept of "midichlorians". Are they just an indicator of Force sensitivity, or do they actually create the Force itself? Canon gives no information either way. Wookieepedia says they're just sensitivity indicators, and one theory suggests that the Force creates midichlorians (and not the other way around), but it's another source of intense debate.
** Many fans believe that Anakin didn't believe Palpatine's conspiracy theory that the Jedi were trying to take over the Republic, but he went along with it anyway because Palpatine had something he needed. The films are ambiguous on this; James Luceno made that canon in the ExpandedUniverse.
** Shim Skywalker apparently [[MysticalPregnancy became pregnant with Anakin despite being a virgin]]. The movies never explain ''how'' this happened outright, other than a vague line about him possibly being "conceived by the Living Force". Many fans latch on to Palpatine's story of Darth Plagueis, a Sith lord who could "create life"; they thus believe that Plagueis' experiments with midichlorians resulted in Anakin's conception.
** The vast ExpandedUniverse can sometimes be contradictory, not just with the films, but also with each other. Fanon tries to keep everything straight, but it's not that successful with that. Its canonicity was never very strong, but ''Film/TheForceAwakens'' and its sequels have been largely confirmed to override it anyway, making everything here even more dubious.
** Another theory is that Darth Vader avoids setting foot on Tatooine because he's afraid to face anything that reminds him of his past life as Anakin Skywalker. It's never addressed in the films, but it does explain why Obi-Wan sees no problem with hiding Luke there, and why Luke never bothers to change his surname; Darth Vader would never come to get Luke himself even if he knew he was there.
*** Anakin in the Expanded Universe frequently calls Padme "Angel" as a term of endearment, even though he only ever called her an angel once in the films.
*** There are all sorts of strange theories regarding family relationships, including that [[FamilyRelationshipSwitcheroo Anakin is really Ben's father]], Palpatine has some relationship with Mara, and Luke lost his virginity to Leia right after the Battle of Yavin (so before they knew they were [[BrotherSisterIncest brother and sister]]).
*** Fans have created all sorts of inconsistency in interpreting sexuality in this universe. The Jedi are often shown as being completely {{celibate|hero}} ([[WordOfGod George Lucas has claimed otherwise]], but also said Jedi can't "form attachments", which implies something most fans don't want to deal with). {{Slash|fic}} fans have gone all over the place on the universe's stance on homosexuality, ranging from EveryoneIsBi to practically puritanical attitudes. Bioware caught flack for [[HideYourLesbians Juhani]], as although she was written as a lesbian, it's not so clear in the game itself. Karen Traviss settled this with Mandalorians, at least, writing them as simply not giving a shit.
*** Most fans believe that Luke was under the influence of the DarkSide during the ''Dark Nest'' trilogy.
*** Fans have assumed that the word ''[[PardonMyKlingon kriff]]'' -- largely undefined in the EU -- has something to do with sexual intercourse. Probably because it's usually used as a stand-in for "fuck".
*** Several fans assume that Jaina Solo takes the title "Galactic Empress" after her husband Jagged Fel becomes the Emperor of the new Galactic Empire. We haven't seen much of Jaina and Jag's life beyond their marriage, and details about Jag's reign as Emperor are rather scarce. Most fans agree that Jaina and Jag are likely to be RoyalsWhoActuallyDoSomething, since both are decorated fighter pilots, Jaina is a legendary Jedi, and she learned a lot from her mother Leia's example, and she's not likely to sit on the sidelines while her husband runs the Empire.
* ''Film/TheBigLebowski'': A popular theory among fans is that Donnie is Walter's imaginary friend. This doesn't make much sense, as the Dude also acknowledges him a few times during the movie, both characters [[spoiler:go to a funeral home after he dies]], and other characters (including the Stranger, the Jesus, and Gary the bowling alley bartender) acknowledge him as well.
* ''Film/TheUsualSuspects'': There are a number of fan theories that identify Keyser Soze as any member of the cast you care to name. In the director's commentary, the filmmakers express puzzlement over this phenomenon, saying they felt the end is pretty clear.
* In TheFilmOfTheBook of ''Film/PrinceCaspian'', a geeky boy attempts to flirt with Susan at the train station in the first few minutes of the film. A small group of fans have grown attached to him, calling him Warren.
* The ''Film/LordOfTheRings'' films gave us [[http://knowyourmeme.com/memes/figwit Figwit]], the sexy elf from ''The Fellowship of the Ring''. He was noticed by fangirls and anyone else who got bored during the Council of Elrond scene; they adopted him and called him "Figwit" as [[FunWithAcronyms an acronym]] for "Frodo is great -- who is that?" He's also played by Bret [=McKenzie=], whom viewers may have recognized from ''Series/FlightOfTheConchords''. As a nod to the fans, he reappered in ''Return of the King'' (to much {{squee}}ing), and [=McKenzie=] was given another role in ''Film/TheHobbit'' trilogy, as Elrond's personal herald "Lindir" (meaning "singer").
* Some fans like to put both ''Film/EventHorizon'' and ''Film/TheChroniclesOfRiddick'' in the ''TabletopGame/{{Warhammer 40000}}'' universe. In ''Event Horizon'''s case, it's quite plausible to put the film sometime in the Dark Age of Technology, and the events line up well with everything we know about the Warp.
* ''Film/FightClub''
** A surprisingly large number of people sincerely believe that the name of Edward Norton's character is Jack. In fact -- and this is [[LampshadeHanging lampshaded]] in the film -- his true name is [[spoiler: never revealed, although an argument can be made that it is, in fact, Tyler Durden.]] Notably, the novel is a bit more unambiguous about the last point, as it includes a brief scene after TheReveal where the Narrator [[spoiler:shows his driver's license to Marla to prove that "Tyler Durden" isn't his real name]]. The film called him Jack in the script and behind the scenes, but only as a nod to [[spoiler:the ''Reader's Digest'' articles written by an organ in first person discussed in the film]].
** Another popular theory is that ''ComicStrip/CalvinAndHobbes'' is the prequel to Fight Club, with the Narrator being an older Calvin, Marla as Susie, Bob being an older Moe trying to be TheAtoner, and [[spoiler:Tyler as a vengeful reincarnation of Hobbes.]]
* The fandom for ''Film/{{Inception}}'' has unanimously decided that Eames' totem is a poker chip. This is fleetingly implied in the film but never explicitly stated.
* Michael Myers, the antagonist of ''Franchise/{{Halloween}}'', is believed to have [[spoiler:never dies in either of the two original timelines.]] This means that presumably, he has [[spoiler:survived the end of both ''Film/HalloweenTheCurseOfMichaelMyers'' and ''Film/HalloweenResurrection'', the last in each respective timeline.]] The [[Film/Halloween2007 remake]] further suggests that [[spoiler:the filmmakers aren't planning to end either timeline.]] Chris R. Notarile made a fan film based on this theory (which included professional voice actor Creator/TomKane), depicting [[spoiler:Michael Myers' death at age 60, from the rage inside him, as Dr. Loomis predicted in ''Film/Halloween5TheRevengeOfMichaelMyers''. It could fit into either timeline]].
** Notarile made another fan film, which depicts [[Franchise/ANightmareOnElmStreet Freddy Krueger]] [[spoiler:captured by Pinhead sometime after his death in ''Film/FreddyVsJason''. He is then tortured by Jason Voorhees, the mind of Michael Myers, and the presumably deceased soul of [[Franchise/TheTexasChainsawMassacre Leatherface]], with Pinhead telling him "Your reign of evil is now over."]] This contradicts ''Comicbook/FreddyVsJasonVsAsh'' and its sequel, but these are an alternate sequel to ''Freddy vs. Jason'' itself; the "main" sequel, ''Film/JasonX'', can't take place after ''Freddy vs. Jason vs. Ash 2: Nightmare Warriors'' because [[spoiler: history is altered to prevent Freddy's transformation into a dream demon, thereby preventing him from resurrecting Jason at the end of ''Film/JasonGoesToHellTheFinalFriday''.]]
* In ''TheBoondockSaints'' fanon, it's generally agreed that Connor is the older twin.
* HighSchoolMusical fanon:
** If Chad is not dating Taylor, he's dating Ryan 99% of the time. Probably has something to do with the [[HoYay sexy baseball scene]] in the second movie. Even fans who don't ship Ryan/Chad assume ''something'' went down in the locker room after that baseball game, not helped by the fact that they're [[SexyShirtSwitch wearing each other's clothes]] in the next scene.
** Sharpay often has a cutesy nickname that her mother calls her by, to go with Ryan's "Ducky".
* Many Creator/QuentinTarantino fans theorize that the events of his several films are linked together in some way.
** One popular theory is that at least some of the events of ''Film/PulpFiction'' occur on the same day as the bank heist in ''Film/ReservoirDogs''. In particular, the reason why there are no cops around to stop Jules and Vincent while they're driving around covered in blood is that they're too preoccupied with the heist and its disastrous aftermath.
** Another theory is that ''Film/PulpFiction'' is a direct sequel to ''Film/ReservoirDogs''. This theory suggests that the the [[{{Macguffin}} mysterious briefcase]] in ''Pulp Fiction'' contains the diamonds from the heist in ''Reservoir Dogs''. This has some basis in fact, as WordOfGod has confirmed that the briefcase was supposed to contain diamonds in the original draft of the script.
** The theory that ''Film/KillBill'' is [[ShowWithinAShow an action movie that Mia Wallace starred in during her time as an actress]] -- possibly even a reworked version of her failed ''Fox Force Five'' TV pilot -- has recently caught on with Tarantino fans.
* Many viewers of ''Film/{{Avatar}}'' believe [[spoiler:Eywa is manipulating ''both'' sides of the conflict to achieve her ends of getting rid of the RDA.]] This is based on absolutely no canonical evidence whatsoever. She doesn't even [[spoiler:visibly interfere until Jake takes some time to explain the situation to her, and the Na'vi are about to ''lose'' their decisive battle, when she could've just ZergRush'd the RDA at about any time.]]
* The ''Film/StarTrek'' reboot caused some issues in that timeline, as WordOfGod was explicit that it was an alternate timeline. Fans have their own ideas as to how those timelines differ.
** One theory is that Kirk was sent to Tarsus IV after the "car incident" and thus was present for the massacre on the colony, just as the Kirk of the "main" ''Franchise/StarTrek'' timeline was. It's not unusual for this to be a profound influence on his character in fic. The notion has also crept in that nu!Kirk studied under [[Series/StarTrekEnterprise Hoshi Sato]], who was said to be on Tarsus IV at the time of the massacre.
** The vast majority of reboot fanfic writers depict Kirk's stepfather as an alcoholic, ultra-abusive, and even a child molester. His mother is also often written as depressed and emotionally distant.
** Fanon also suggests that Kirk is allergic to a large percentage of medications, basing it on ''both'' timelines; we see his allergy to eye medication in ''Film/StarTrekIITheWrathOfKhan'', and we also see his strange reactions to everything Bones gave him in the 2009 film.
* ''Film/{{The Avengers|2012}}'' has so much "headcanon" that there's [[http://theavengersheadcanons.tumblr.com/ Avengers a whole site]] dedicated to this trope. The character Hawkeye, though, attracts the most theories, many still inspired by the mainstream comics. They include that Clint was a CircusBrat with a criminal record (like in his comic backstory), served in the U.S. Army or else some kind of law enforcement division, is a single father with a young child, is or once was dating (or even married to) [[ComicBook/{{Mockingbird}} Bobbi Morse]], that Bobbi Morse is the mother of the aforementioned child, and many more. Some fans of ''Film/TheBourneLegacy'' even invoke the ActorAllusion to suggest that this film is Hawkeye's origin story; both characters are played by Creator/JeremyRenner.
* ''Franchise/PlanetOfTheApes'': It's widely accepted that Zira and Cornelius coming to the past and Caesar's birth there altered the 'verse's history, greatly speeding up the ape revolution and making it happen much earlier than the one that led to the events of the [[Film/PlanetOfTheApes1968 first film]]. This may also mean that the aftermath of ''Battle'' is different from the one in the original timeline, and that the world might not have been destroyed as it was in ''Beneath''. A "closed loop" theory also suggests that anger at Caesar led to him being erased from ape history later on, leading to the scrolls Zira and Cornelius read having Aldo as the first to say "no".
* A common theory regarding the ContinuitySnarl between ''Film/XMenFirstClass'' and ''Film/XMenTheLastStand'' is that the Xavier who visited Jean Grey was, in fact, a psychic projection.
* In ''Film/BillAndTed'' fanfics, if either of boys' biological mothers' whereabouts are mentioned, typically Bill's left him and his father, and Ted's mom is dead, going along with the fanfic trend of making him [[TheWoobie a Woobie]].
* ''Franchise/{{Godzilla}}''
** In fan works and non-{{canon}} ExpandedUniverse stories, it's fairly common to portray [[Film/GodzillaVsBiollante Biollante]] as an example of GaiasVengeance with an empathic connection to the HiveMind of [[MotherNature the Earth itself]]. In the actual films, this was never the case; Biollante was just a single mutated plant with individual sentience, thanks to being cross-bred with the DNA of a human girl.
** Fan works tend to portray Anguirus as the [[BadassGrandpa oldest]] {{Kaiju}} in the ''Godzilla'' universe, and it's not uncommon to portray him and Godzilla as being VitriolicBestBuds with a grudging respect for each other, reflecting their long history together. This has ''some'' loose basis in {{canon}}: Anguirus was the first {{Kaiju}} that Godzilla ever faced (back in ''Film/GodzillaRaidsAgain'', the second movie in the series), he was said to be a mutated dinosaur from an extinct species, and he and Godzilla ''did'' team up on a few occasions in the Shōwa series. Still, nothing in the series ever indicated that he was actually physically older than any of the other monsters, and his relationship with Godzilla never seemed to be especially close.
* Several ''Franchise/IndianaJones'' fans seem to consider it {{canon}} that Indy becomes immortal following the events of ''Film/IndianaJonesAndTheLastCrusade'' after drinking from the Holy Grail. Among other things, this provides a handy explanation for how he survives the infamous fridge-nuking in ''Film/IndianaJonesAndTheKingdomOfTheCrystalSkull'', and how he manages to survive into the present day as seen in the framing sequences in ''Series/YoungIndianaJones''.