Due to the vagueness (or, more accurately, inaccessibility) of Street Fighter's storylines, as well as incorrect facts/mistranslations printed in game manuals, the Street Fighter series has quite a lot of fanon material that is taken as canon by many.
The fighting style of Ryu and Ken that has been passed down to them by Gouken has never been named in the Japanese versions of the games. A lot of Street Fighter fans outside Japan have misinterpreted the term ansatsuken (literally "assassination fist") as the name of their art. However, ansatsuken is actually a common Japanese term in fiction and in fact, Gen's unrelated fighting style has also been referred as an ansatsuken as well in the series. The fighting style of Ryu and Ken is not an ansatsuken itself, but the three special techniques they use (the Hadoken, Shoryuken, and Tatsumaki Senpukyaku) were originally part of the assassination art that Gouken and Gouki learned from Goutetsu before Gouken refined them into non-lethal purely defensive techniques. Capcom USA's localization staff hasn't been helping matters either, often referring to Ryu and Ken's style "Ansatsuken" in source material (ignoring its use of the word as a general term).
That the character Akuma is a demon, or at least a generally evil character; in fact, he is more of a Blood Knight. Demon is more of a description of how he fights (not to mention the literal translation of his name).
Akuma's whole goal (other than to turn Ryu to the "Dark Side") is to find powerful martial artists to fight and kill. He is literally a serial killer. He also killed his brother (well, sort of) and his sensei — though the latter happened in the context of a Duel to the Death rather than on a mere whim. He may have killed Bison, but recent revelations tell us that probably it didn't quite happen like that: according to Street Fighter IV and its tie-in OVA, Akuma did attempt to use the Shin Goku Satsu on Bison, but Bison beat him to the punch by killing himself first. However...
It should also be said that while Akuma has killed or attempted to kill several martial artists over the course of the series, he's not a mass murderer who roams aimlessly killing anyone he crosses paths with and will call off of the fight against his challengers if he believes they're either not ready to face him or in a disadvantage: this is why he spared Gen, who was dying of leukemia, in Alpha 2; earlier sources also state that he knocked Ken, who discovered Gouken's body almost immediately after his final duel with Akuma and then hounded Akuma, away instead of killing him). Overall, Akuma adheres to a very strange honor code as a warrior and went after Bison in II because he thought Bison was misusing his power. On top of this, Akuma is not above petting the dog, as he even (circa Alpha) saved a boy who wandered into his cave and subsequently bought goods from him. One could argue thatlabels such as "good" and "evil" don't apply to Akuma and that he is only "evil" in the antagonistic sense (just ask Ryu), not the moral one. Of course, Character Exaggeration in crossovers and other adaptations throw this out of the window and strip Akuma of any complexity he hasunder theObviously Evilsurface.
Several characters are given first and last names (originating from the live-action movie and American cartoon). Ryu and Chun-Li's surnames are Hoshi and Xiang/Zhang respectively, Sagat's first name (Victor), and Guile's full name and rank (Colonel William F. Guile). Dhalsim is considered his last name since he was referred to as Dr. Dhalsim in the movie.
There's also the belief that Ken defeated Ryu during the events of SFII. This one is a bit more understandable: during their last battle (in Alpha 2), Ryu was too hung up on his previous battle with Akuma and the Satsui no Hadou raging within him to focus, allowing Ken to best him quite easily. After giving Ryu a pep talk and bequeathing his hairband to his buddy (this would become Ryu's trademark red headband in all appearances chronologically following Alpha 3), Ken vows that he won't marry his then-girlfriend Eliza until he defeats Ryu again in a fair, decisive match. By the time of III, Ken and Eliza are shown to be married and have a young boy named Mel, whereas IV (roughly one year after II) depicts Eliza's pregnancy in full.
It's accepted by many that Mike from SFI and M. Bison/Balrog are the same fighter, but Capcom can't confirm this for legal reasons. (i.e. the character being an expy of Mike Tyson.)
In the numerous dojinshi works revolving around the Touhou video game series, the fans have almost unanimously turned several characters into chew toys (Alice Margatroid, Hong Meiling, Reisen, Youmu...) regardless of whether or not anything in the official works points to such a fate. In Alice's case, the fanon version is almost the complete opposite of the canon version.
Interestingly enough, some fanon aspects have been confirmed in canon. The character Keine, while originally only shown as a "protector of the human village" with some connection to history through her abilities, was almost always portrayed as a schoolteacher in dojinshi — and then was confirmed as being a teacher in the second book. The series' creator is extremely supportive of fanworks of all types, so it's very likely a case of fanon turning into canon.
Fanon often posits Yuuka and Flandre to be insane mass murderers (or at least, the latter would be if unleashed), from Yuuka's genocide jokes in Mystic Square, to Flandre's stated-but-nebulous insanity and destructive power. Koishi also gets this treatment on occasion from doujin artists who believe reading a subconscious can drive one to insanity.
Two nameless miniboss type fights from The Embodiment of Scarlet Devil were later named after their fanon nicknames by ZUN: Daiyousei (lit.: greater fairy) and Koakuma (lit.: little devil). They haven't had any canon appearance since then but are used consistently as foils for related characters (Cirno and Patchouli, respectively) in fan-works.
In Super Mario Bros. fandom, the tendency to use the The Super Mario Bros. Super Show personalities of the Koopalings paired with the games' names for them is a pervasive piece of fanon, despite allusions to their Canon personalities in Super Mario World. In fact, these personalities are so popular that quite a bit of SMB fanfic is exclusively about the Koopalings!
Another example is the widespread belief that the Mario Brothers originated in Brooklyn and ended up in the Mushroom World through a freak accident. This idea seems to have originated in the Western cartoon as well. Meanwhile, the Yoshi's Island series of games flat-out state that the Mario Bros. were born in the Mushroom Kingdom (although, if this is true, one has to wonder where all these humans—and their thick Italian accents—are coming from). Of course, there's nothing yet prohibiting the idea that they may have moved to Brooklyn at some point in their lives. Maybe the events of Yoshi's Island convinced the Mario Brothers' parents that the Mushroom Kingdom was too dangerous of a place to raise kids?
That seems to be what they want you to think, that they moved to Brooklyn - Mario growing up in Brooklyn is mentioned in passing in some of the games (Mario Party 5, for instance), long after Yoshi's Island was released.
Let's not forget the idea that the "modern" Mario, born in the Mushroom Kingdom as seen in Yoshi's Island, is the son of Jumpman, the "original" Mario.
This seems derived from Rare's Donkey Kong Country series - in which DK's elderly father Cranky claims to be the original Donkey Kong who fought with Mario.
The Mario Bros. having the actual last name "Mario." While mentioned in the cartoons and the movie, this was never stated in the games. The chief argument for this is that any famous group of brothers (Jonas, Marx, etc.) aren't referred to by the most famous one's name.
Another common belief is that their last name is Jumpman.
Shigeru Miyamoto supposedly said that they were called the Mario Bros. because Mario is the frontman of the two, and that they don't have last names. However, Nintendo Power once claimed that their last name is Mario, so nobody knows...
Whether or not Bowser has a last name - in Japan he's called "Koopa", but has been localized as "Bowser, King of the Koopas" since the instruction manual for the first game. The "King Koopa" name was used in the Super Show, and even after Mario 3, follow-up cartoons (and the movie) kept the name. It was clarified once or twice in The Adventures of Super Mario Bros. 3 ("I'm Bowser Koopa. King Koopa to you!"), but never in the games, which only makes things more confusing:
The Koopalings are all surnamed "Koopa" - but this arises from the localization. In Japan the characters have never been referred to as Bowser's children and are only referred to by their first names (confusingly, taken from the U.S. localization of Super Mario Bros. 3). They're even renamed "Bowser's lackeys" in the English manual for New SMB Wii. Don't get us started on Bowser Jr.
Since one of the Koopalings' names is "Morton Koopa, Jr," following the American version of events suggests that Bowser's full name would have to be Morton Bowser Koopa, Sr. That or their mother was named Morton, which is even more disturbing. This, of course, assumes that Morton Senior wasn't Morton Junior's grandfather, or they don't have an uncle named Morton... basically, there has to be a Morton in that family tree somewhere.
From the Super Mario Bros. instruction booklet: "One day the kingdom of the peaceful mushroom people was invaded by the Koopa, a tribe of turtles famous for their black magic." So, the Koopa is the name of the species. Bowser is their king.
As for Bowser's wife, an issue of Nintendo Power UK mentioned that her name was Clawdia. Since then the fandom has embraced this, using her in fanfics as the Koopalings' (and sometimes Jr's) mother.
Most fans believed the manual for Super Mario Land 2 stated that Wario hired Tatanga to kidnap Daisy as a distraction when neither the game or the manual mentioned such a thing. This was even listed on the Other Wiki for a while.
Most SMB Fanon originates from Lemmy's Land.Lemmys Land has a fairly large, mostly serious Fan Fiction section where most of the internet's SMB fanon spawns, while the "Scribbles" section is usually there to make a laughing stock of every Mario character. The "Interviews" often go both ways.
To parallel Mario and Luigi, Wario and Waluigi are brothers.
In Mario Party 5, pairing the two creates the team name "Wicked Bros." The thing that makes this only a possibility and not definitive proof? Less/non-related characters can also sport names to the tune of Adjective Bros. Really, the surprising thing is just that Wicked isn't usually used as their last name based off this.
The trophy gallery in Super Smash Bros. Melee claims that Wario and Waluigi's relation to each other is unknown.
Additionally, there's the tendency to assume that the Mario Bros. and the, uh, Wario Bros. are cousins. Officially, Mario and Wario have a rivalry that stretches back to childhood (when Mario was actually Wario's antagonist), but any relationship between the Good Bros. and the Bad Bros. is mostly speculation.
Various official sites for Nintendo games have actually called them brothers, but it constantly flip-flops.
Another common assumption among fans is that Wart from Super Mario Bros. 2 is Bowser's brother, who was transformed into a frog somehow (the exact method varies from fan to fan, most being either a lab accident or that he was transformed by Bowser in a bid to get the throne).
Elsewhere in the 'verse, the Wario Land games have a recurring Pirate Girl named Captain Syrup. The games have never confirmed the assumption that her first name is Maple.
Long story short, the Mario series is anything you want it to be. In fact, it DEFINES fanon with every passing game.
One item that is assumed, but only ever shows up in spin-off games, is best expressed by Brentalfloss' "Mushroom Kingdom":
Mario! He gets mad superpowers
from eating leaves and flowers...
Mario's power-ups in most of the series have usually been shown to activate on contact, and are also depicted this way in Super Show and it's successors.
While Sonic games aren't particularly known for deep plot-lines, one persistent fan theory would make Shadow, the series' resident Sonic clone, literally a copy of (Super) Sonic, despite having been genetically engineered fifty years before the series began. In Sonic & Knuckles, Sonic faces off against... well, Knuckles in the Hidden Palace Zone, a secret holding place for the Master Emerald. In the background of the battle is a mural that depicts a yellow, hedgehog-shaped thing flying and fighting a giant robot over the Master Emerald in a somewhat subtle bit of Foreshadowing, created thousands of years earlier by the ancient Echidna civilization. Later in Sonic Battle, reading the diary of Professor Gerald, Shadow's creator, shows that the man has spent a great deal of time researching the very same Echidnas that made the above mural. This is insignificant on its own, until one considers some of the similarities between Shadow and Super Sonic; both hover above the ground in place of running, both have tussled, unkempt-looking spines, both have red eyes, both are immortal (though in different ways), and both possess extraordinary control over the Chaos Emeralds. Although the implications of Sonic being a warrior of prophecy and Shadow being a copy of him via that prophecy could easily become one of the deepest aspects of the entire plot, it unfortunately doesn't seem like it will be capitalized on.
Suggestions based on this are that Professor Gerald was not trying to copy history; rather he believed the mural was indeed of a warrior of prophecy and in his arrogance thought he could fulfil the prophecy, which was why he created Shadow as a hedgehog of all creatures.
Everybody knows Sonic's hydrophobic... except he isn't; he has a normal fear of drowning considering he can't swim. Sonic's "hydrophobia" is only shown in one episode of Sonic Underground and has been expanded to a few episodes of Sonic X: he wouldn't even go to the seaside when he had a choice, but quite a few Segasonic sources even say he loves the seaside.
To be fair, after Labyrinth Zone, we wouldn't be surprised if it made him hydrophobic.
Also, thanks to Sonic and the Black Knight having Shadow as Lancelot and Silver as Galahad, many fans considered the similarities between the two (certain abilities, personality traits, species and chest hair) and the fact that Shadow is immortal while Silver is from the future, and decided that Shadow is who Sonic Team has in mind as Silver's eventual father.
A major point made is that the Round Table had lots of good, strong and famous knights, and Silver, not being a part of the story itself, could have been any one of them, but Sonic Team chose Galahad, son of Lancelot.
They get a 'special' winning animation in the Sohoi Olympic Games too, which is intended for characters with some kind of relationship. There's a lot of father-son feeling in theirs, with Silver trying to copy Shadow and look tough, when most of his winning poses have him floating around like a kid.
One relatively decent self-insert character in SatAM Sonic the Hedgehog fanfic, Bookshire Draftwood the elderly raccoon doctor, grew so popular and filled such an obvious hole in the cast that he actually became part of fanon. Archie Comics subsequently tried to make their own doctor character, Dr. Quack, but he was considerably less sympathetic and endearing and thus wasn't so well-received by the fanbase.
Elsewhere in Sonic the Hedgehog, the game Shadow the Hedgehog gave the titular character the ability to carry and use weapons, usually guns of one type or another. Some fans had already decided that, because (in canon) someone very important to him was shot, Shadow hated guns and would never use them.
To be fair, reasons for this assumption also included his rather pronounced superiority complex and the fact that he could throw Chaos Spears around with his mind, thus rendering common ballistic projectiles somewhat redundant.
Also G-Merl's name (alternatively G-mel or Gemerl) is fanon; Sonic Advance 3 and Word of God implies that he's really Emerl from Sonic Battle. Also in Sonic Unleashed, Eggman's robot sidekick (named Orbot in Colors) is given the fanon name Ergo, because he says "Ergo" a lot.
There was a theory going around for a while that the Babylonians built Emerl, due to the text calling the awakened Gizoid a god at one point, and the legend stating that Babylon was destroyed by an angry god for their hubris. Naturally, Chronicles laid this one to rest.
In a more minor example from the Sonic comics, a fan artist depicted Prince Elias as having a ponytail in erotic art of him, prettying him up a bit. Now it's rather easy to find fanart of Prince Elias as having a ponytail, which has led to some folk who are fans of the comic continuity without reading the comic itself (Gushing about shows you don't watch?) finding themselves surprised when official art 'cuts off' Elias' ponytail.
Sonic the Hedgehog (2006) created a bit of a Continuity Snarl with Ensemble Darkhorse Blaze the Cat; in Sonic Rush (her introduction) she was supposedly from another universe, while in 2006, she was from the future. However, in the end of 2006, she was sealed in another dimension. While 2006 ended with a Reset Button, fans attempted to reconcile the two plot lines by stating that the dimension Blaze sealed herself in was the one from Rush. To be fair, the game does somewhat imply this.
The cult classic NES game The Guardian Legend has a great example of Fanon. In the original Japanese game, the Guardian of Earth was apparently named Miria in the instruction manual, but the English language release left her unnamed. In the years after its release, the game saw a few fanfics put up online, one of which referred to the Guardian as Alyssa. For some reason, this caught on, and she's been referred to by that name by almost any fan of the game since. Look up TGL on almost any retro gaming site now and it will probably mention Alyssa.
Occasionally, the fact that Ike canonically departs from Tellius at the end of Radiant Dawn for parts unknown is used to have him cross over into other FE universes (or new ones entirely). To a much lesser degree, this is also used for MarktheTactician (the Player Character from the seventh game), who also disappears after the events of the game, despite being named the godparent of either Roy or Lilina and promising to meet up again with Eliwood or Hector in the future.
Fire Emblem Awakening does something similar. In one of the SpotPass sidequests Chrom meets a character named Priam who wields Ike's sword Ragnell and claims to be the descendant of the "Radiant Hero" who traveled to Archanea from another world. Many Fire Emblem characters, including Marth, Ike, and Roy also all appear in Awakening as DLC characters, though these are apparitions known as "Einherjar" modeled after ancient heroes rather than the actual characters themselves. Additionally, the Avatar and/or their child Morgan are hinted to have a connection to the Tactician from Blazing Sword, if not be the same character outright. Similar clothing aside, Lyn has a hunch that the Avatar and Tactician might be one in the same (she recognizes him on sight and feels even stronger about her convictions upon learning the Avatar woke up in a strange place with no recollection of how they got there, just like her Tactician; the player can either confirm or deny her suspicions), whereas Morgan's name in the Japanese version of Awakening is Marc. Both characters also have access to the Grandmaster class, which was the title awarded in the Japanese version of Blazing Sword for obtaining the highest Tactician ranking.
Marth is also believed to be arrogant and narcissistic, while Roy is believed to be hyperactive and dumb. Their real personality is a humble, just, and intelligent ruler, like many Fire Emblem lords. Similarly Ike is believed to be a dumb meathead while he is actually quite intelligent. (Awkward Zombie is probably to blame for that.)
Thanks to The Future Past DLC chapters in Awakening and its use of both the male and female Morgan as bosses, fans have begun to latch onto the idea that the Avatar actually had twin children instead of a child of the opposite gender, so as to use both Morgans. The female Morgan keeps her name, whereas the male one gets his Japanese name, Mark.
Speaking of Super Smash Bros., it was a very popular idea (save one notable exception), before Brawl came out and gave the Smashers an actual world they lived in via the Subspace Emissary mode, that the Smashers lived in a Reality Show/Big Brother-esque giant mansion, with Master Hand presiding over them all as the lord of the mansion and being some kind of God figure that occasionally came down to play with them all.
A fairly large portion of the fanon community refers to Klutzy as a girl, even though Klutzy is referred to as a boy in canon.
The Warcraft setting of Blizzard fame has also been repeatedly subjected to fanon, and every game release (and now, every other patch release in the MMO World of Warcraft) was filled with wild speculation from fans — speculation that would often evolve into fully written documents on the subject, carefully doctored images, and even their own Wowpedia pages. Some of the least grounded and most fan-developed theories that took fire over the internet included naming the high elven gods (this has happened TWICE, despite many canon sources acknowledging that high elves follow the Holy Light, when they even care about religion), the new Alliance race in the Burning Crusade being night elf spirits possessing the bodies of demons, the second WoW expansion being focused around the Maelstrom with naga and pandaren as races (it proved to be Wrath of the Lich King instead). Blizzard forums also frequently suffers hostile reactions from fans when the company fails to meet fanon expectations — pretty much every patch, since the company has a history of surprising its players that predates WoW.
Perhaps the prime example of Fanon was the belief that the Forsaken were outright unable to use the Holy Light. Fans vehemently believed this was part of the games lore and was cited in the RPG books when in truth the citation didn't even exist in the RPG. How much they deal with it is another matter (the starting zones hinted at a darker religion that was spelled out in the non-canon RPG), but the point is that they can.
Appendix III, a section of the old Warcraft Tabletop RPG on thinking up ideas for players to use DnD monsters in the Warcraft setting had fans believing Forlarren and leprechauns were canon to Azeroth for years!
Another interesting bit of fanon is the Lich King's power. In canon, the Lich King has shown three major traits: The Chessmaster, a necromancer, powerful. Ask a Warcraft fan pre-WOTLK, and they would tell you the Lich King could one shot the Old Gods, Kil'jaeden, and probably the Titans themselves. His fanon power was so legendary that the very thought that the players could even threaten his plans seemed like a sin against humanity. It's been guessed that by the end of the expansion, after Arthas spends much the war running and getting his strongest warriors killed, that Blizzard purposely made the Lich King fail so much was because the fans turned him into a god.
Troll Voodoo is often misunderstood. Several players think the Darkspear no longer practice voodoo because of one of the troll greetings being "stay way from the voodoo", but actually they still do practice it. Vol'jin, leader of the darkspear, is amongst its most notable users. Some players think it is related to warlock magic when actually it is more connected to Shamanism and priests(the former having received Witch Doctor and Shadow Hunter spells such as Hex and healing wave from Warcraft III). It is not evil either as often thought, instead it is more a neutral source of magic.
The idea that draenei have two hearts has cropped up in several fanfics by different authors.
The eredar spy Talgath has no official title. However, "Hand of the Deceiver" seems to have stuck so well that it was actually on his Wowpedia page for some time.
A recent example was a doctored (and supposedly leaked) image of Duskbringer, Risen Champion of the Forsaken, who was believed to be a famous champion of light and good Uther the Lightbringer, who was risen as one of the Undead Forsaken. This didn't sit well with most fans and numerous lore reason was brought up as to why Uther should simply stay dead. In the end the image was a fake, but still a good example of Fanon coming into play.
One bit of fanon that is often confused with canon: Deathwing attacking Stormwind to retrieve the severed heads of Nefarian and Onyxia. While it would explain how the two of them are suddenly back after being dead for several years, this has never actually been stated in lore. In fact, no official explanation for the attack on Stormwind beyond "The beast is insane!" has ever been offered.
It had long been debated that the world was destroyed at the end of Final Fantasy VII. There was a serious outcry from the fans of that theory that Square was actually violating canon when they announced the Compilation of Final Fantasy VII, which includes two directsequels that explicitly show the world alive and well.
In the same vein, there's a tiny amount of ambiguity at the end of Final Fantasy X as to the fate of Tidus. Despite the ending credits showing Tidus arriving in Spira again, before the announcement of the sequel, many fans argued that the scene was only metaphorical. This was not enough to stem the outcry that Final Fantasy X-2 was retconning what they believed to be "one of gaming's greatest tragedies" by depicting Tidus' return to Spira in the exact same FMV clip they used in X and thus proving it wasn't supposed to be metaphorical at all.
In Final Fantasy X-2 fanfiction (if it's not just handwaved) Shuyin is generally held to be the real-world prototype of Tidus. The parallels between their love lives are usually dismissed as coincidental, though.
The Ultimania notes that Tidus could have been based on the memories the Fayth dreaming Dream Zanarkand into being had of Shuyin, but also notes that the fact that people in Dream Zanarkand had parents and children complicates this.
Many Final Fantasy VIII fans believe that Raine's maiden name is "Leonhart," as a way of explaining where Squall's surname came from when his father is named Laguna Loire, citing the general dislike the residents of Winhill display towards Laguna as a reason they might have given Raine's name instead of Laguna's when delivering Squall to the Kramers' orphanage. The game itself never gives Raine's maiden name; her full name is only given after she's married.
If you've spent any time reading fanfiction for this game, you will have seen characters using Hyne's name as a blasphemy in various ways (e.g. Hynedammit). Hyne is never referred to like this ingame. In fact, it's entirely possible to get through the whole thing without seeing his name at all, and when you do find the story, it's pretty obvious he's not the kind of guy most people would worship. What people do use for blasphemy? "God." Even "Godspeed." Or, if you're Squall, "GOD!!!!!!!"
In Kingdom Hearts, due to the general vagueness of a lot of the inner mechanics of the universe, a couple theories have become embraced by the fandom.
One notable one is the explanation for Kairi's keyblade. In game, Riku just gives her a keyblade out of nowhere during a sequence in Kingdom Hearts II, which she uses during the sequence and seems to lose it by her next appearance. Sora gets a second keyblade in many of his Drive forms. By connecting these two details together, the assumption that gets made is that "copy keyblades" can be made and either used in the off-hand or given to someone else, with it vanishing when it's no longer necessary.
This was Jossed in Birth by Sleep, as Kairi's Keyblade (named Destiny's Embrace) was the result of an unintentional Keyblade Inheritance Ceremony between Aqua and a young Kairi, whereas Sora and Roxas derive their second Keyblades from Ventus' heart within Sora (contrary to popular belief, Roxas absorbing Xion in Days was not the reason behind Roxas or Sora's dual-wielding). The question of how Riku obtained that Keyblade for Kairi, however, is rife for theories, including a popular notion that Riku went to the Realm of Darkness and obtained it from Aqua herself off-screen during either Days or II.
Kingdom Hearts II, especially, has become the manifestation of Het is Ew. It is said that there are two distinct parts of Kingdom Hearts fanon: the "fanboy part" where everyone is a badass that can hold their own in battles that would make Goku and Vegeta cringe, and the "fangirl part" that consists of a castle full of gay Organization XIII that spend their time playing pranks on each other and having sex.
Because most of the Organization XIII members have little in the way of character development, fans have developed their own personalities. Roxas is pretty and innocent, Larxene is a total bitch, Marluxia is totally girly, Luxord is British and snarky, Demyx is ditzy, Axel is mischievous and perverted, Saix is alternatively crazy or a puppy (or both), Zexion is snooty, Lexaeus works out a lot and is rather dense, Vexen is a mad scientist, Xaldin is sadistically cruel, Xigbar is either a cool war veteran type or a little kid, and Xemnas is their mysterious boss who just wants to be alone most of the time. Surprisingly, most of that seems confirmed by 358/2 Days.
As for their backgrounds before they were Nobodies, it's very common to write Demyx as either a merman from Atlantica or a rockstar.
Naminé, like her "other self" Kairi, never had all that much character development in the games she appeared in. A lot of fangirls, on the other hand, latch onto her for Fanon, often making her the Yaoi Fangirl to the other Nobodies, or to Sora and Riku.
The conviction some fans have that members of Organization XIII have feelings and that Sora is a monster for opposing them. Nobodies do not have hearts. This is firmly established in Kingdom Hearts II with members of Organization XIII confirming they don't have hearts or emotions. The only exceptions to this seem to be Roxas and Xion (from their connection to Sora), Naminé (due to being a "special" Nobody due to unusual circumstances regarding her "birth"), and Axel (from the time he spent with Roxas).
They do, however, have memories of feelings, and they still retain desires, as in, the desires to get their heart back. So those who insist that the nobodies are all cold and evil are not necessarily correct, either. Demyx, for example, still seems to be friendly, and only attacks Sora when he is provoked. Demyx also seems to believe that he can feel.
And to twist the knife further, 3D reveals that Nobodies can actually grow hearts over time based off of their memories when they were whole. Additionally, Xemnas and Xigbar knew this all along and deliberately lied to the other members to manipulate them for their own ends. Judging by Demyx's words to Sora, the only appropriate response? Oops. Of course, Sora is hardly a "monster" for opposing them, since, hearts or not, he was mostly acting in self defense. On top of this, Sora is visibly shocked and outraged that the other members of the Organization were left out of the loop and ended up dying for a false belief.
Resident Evil in general has a lot of fanon, most of it left over from the pre-RE4 years when Capcom seemed allergic to explaining anything. They would make a game specifically to answer a question, which would then confuse several other issues further.
One notable and oddly widespread bit of fanon portrays Chris and Claire Redfield as being part American Indian, which seems to have its roots in George Romero's unused RE screenplay, as well as with the mistaken belief that the name Redfield is of American Indian origins (it's actually Scottish).
The Legend of Zelda has gained quite a bit of fanon, such as Zelda's mother being dead. And Saria, Link's Unlucky Childhood Friend being the one who raised him. This particular bit of fanon is often used as an argument against the Link/Saria ship to boot.
It's also been fanonized that Midna's race, the Twili, are the very same who created Majora's Mask. Midna's helmet bears many of the markings the mask has, not to mention that the Twili were banished to a dark and forsaken realm for trying to use evil magic to attain more power than they were entitled to, which is what the Happy Mask Salesman tells Link about the mask's makers.
Another theory regarding the Twili is that they are what remain of the Sheikah from Ocarina of Time. The two theories are not incompatible.
Due her similar appearance to the Twili and her attire sporting the Gerudo symbol, Veran from Oracle of Ages is usually speculated to have ties to one or both races.
There are two Dark Links: the canon version which is usually a silhouetted version of Link with red eyes, and the fanon version who is just Link wearing black (and often white haired).
The Hero's Spirit/Shade from Twilight Princess is widely believed to be an ancestor of Link, due to his title of "Hero" (which has been given to a few other Links in the series; for example OoT Link is the "Hero of Time", while Wind Waker Link is the "Hero of Winds"), his words that he accepted the role of hero long ago, his choice of words in addressing Link, and implications that he, too, was a wielder of the Triforce of Courage (which is always given to Link, whereas Wisdom goes to Zelda and Ganon gets Power). This is all meticulously detailed here, and Ocarina of Time Link is the frontrunner for the speculated identity of this character.
For that matter, the same could be said for the LoZ timeline. Word of God explicitly stated once that all of the games are supposed to essentially be the same tale that mutated into different versions through corrupted retellings. Think something like a millennia-old game of Telephone. Still, many fans try to come up with timelines that fit every game into a chronological progression. The simplest of these often contain "only" two or three parallel universes (for the games themselves, not counting parallel worlds that actually appear in a game).
Fans have created distinct personalities for each of the Links featured in the Four Swords games, despite them all being Heroic Mimes in the actual games. Green Link is The Hero. He'll be the most focused on defeating the villain and will usually act the most like Link did before the split. Red Link is a Hot-BloodedArrogant Kung-Fu Guy, and often a Comedic Sociopath in comedic stories. Blue Link is silly and lazy, and will usually be the Plucky Comic Relief in serious works. Purple Link, depending on how serious the story is, will either be The Smart Guy or flamboyantlycampy. Interestingly, the Four Swords Adventure manga used this setup, except that Blue and Red were switched.
Many fansites address the Metal Gear Solid 4 character Sunny as "Sunny Gurlukovich", which is her mother's surname. However, the character is only addressed by a single name. According to Metal Gear Rising: Revengeance, her surname is actually Emmerich, as Otacon became her legal guardian between MGS4 and MGR, although that still poses the question of if Gurlukovich was her surname before adoption or if Sunny even had a last name to begin with.
Also, Liquid Snake fans seem to more or less agree on his name. It's James, apparently. Though some folks seem to think it to be John since that was Naked Snake's name.
To explain spoiled bit: Zero was the one to put together the project to clone Big Boss. Since his real name is David Oh and we know Solid's real name is David, some believe that Liquid was named after Big Boss, thus John. Where Solidus' name comes from is anyone's guess. Not that anyone cares about Solidus.
There an alternative theory for this, claiming Liquid's name to be Adam based on the Liquid/EVA exchange in Act 3, going by the notion that David/Zero and Adam/Ocelot were the two closest to Big Boss and practically the ones "responsible" for the Patriots' funding. Solidus, on the other hand, is given John as a name due to being a perfect Big Boss clone, while George Sears is just a false name assumed for his presidency.
This is also going by the idea that Big Boss's real name is John, which is only said to Ocelot in the end. Every other character that refers to him by name calls him Jack, namely The Boss, who doesn't seem like a person to call someone by a nickname. One idea is that Big Boss probably told Ocelot that his name was John was because he didn't want to give his real name away to an enemy, even if he was relatively friendly. Other than that, we don't have direct conformation that his name really is John or Jack, so this is also fanon.
Also, the name given to ocelot was most likely short for "john doe", or the name given to an unidentified military male body. Also, right below this, "Jane Doe" is the same but for a female body. This makes it more unlikely that the actual names were the ones given.
A new theory that has emerged concerning Liquid's real name has emerged with the trailers for Metal Gear Solid V, which is Eli, the boy briefly shown who would conceivably be the same age Liquid would have been in canon, due to their similarities.
Some fans speculate that Para-Medic's full name is "Jane Doe Clark", since she tells Snake at one point that "Jane Doe" is her name in Metal Gear Solid 3. Snake doesn't take her seriously, which cause her to remark that she "wasn't kidding."
The "real names" of the Cobras in MSG3, while they've fallen out of fashion for fan fiction and comic use recently, were fanon for a while. The names, the most used of which was "Michael" for The Sorrow, were supposedly from an interview with Hideo Kojima that found its way onto a French website and were repeated on several Metal Gear FAQ pages. They were used in the fan comic The Cobra Days, and "Michael" was adopted as "Mikhail" for the Fission Mailed online roleplay. Because there is no evidence of this interview in any official sources, the canonicity of these names is debated.
The Cobras have a strange draw for Metal Gear fans to the point where they have been given fanon personalities and some backstory elements that show up in multiple stories, comics, and roleplays. For example, The Fury curses constantly, though he doesn't in the game (granted, he only speaks in one scene), and The Fear, when he has a backstory, is almost always of Roma heritage.
Two bits of common fanon in the Ace Attorney fandom would be calling Manfred von Karma the "Demon God" Prosecutor and that the reason Manfred adopted Miles Edgeworth was partly for an heir, this coming from his aristocratic attitude. Of course, this makes no sense given that canonically Von Karma explicitly screams that he always hated Edgeworth for scarring his arm with the mis-fired gun during the incident that led to Von Karma murdering his father and taking in Edgeworth in the first place. The reason he took him in was to set up a Evil Plan to ruin Edgeworth's life by making him believe he murdered his own father instead of Von Karma.
The Ace Attorney kink meme also has its own fanon, like OCs which are used by different users for different stories, and when a story centers around a pairing other than the usual popular ones, it will normally be taken for granted that the series doesn't really have a canon on shipping... just a lot of Ship Tease.
For that matter, just try and argue Phoenix/Edgeworth isn't canon. Despite them not actually doing anything romantic and Phoenix appearing to not even interact with him for the seven years before Apollo Justice, it's easily the most popular fan pairing. Capcom does not help because they appear well aware of the pairing and love to insert tantalizingly vague dialog into the series even as they introduce more love interests for Phoenix.
In the Apollo Justice era, Edgeworth is assumed to wear glasses. Canonically, we see no sign of anyone from the original trilogy aside from Phoenix Wright and the late addition Ema Skye in AJ at all.
Aside from the shipping wars that dominated the Golden Sun fandom near the start, there were also a couple of random ideas that passed into fanon. For one, there was the idea that the Adepts were naturally averse to their opposite element: Mars (fire) Adepts were afraid of water, Jupiter (wind) Adepts hated the desert, and so on. Nothing in the game really supported this (Garet, the party's strongest Mars Adept, is excited to see the ocean, whereas no one liked trekking through the Lamakan Desert), but aside from the aforementioned, it didn't contradict too much and was a fun way to add personality to the characters, so it stuck.
Several fans have decided that Star Magician is female, due to its sprite having very wide hips.
The gender of NiGHTS from NiGHTS into Dreams... is never stated in any of the games. The first game's manual refers to it as "he, she or it", the second game avoids gender pronouns and gives it a female voice, and Word of God has stated more than once that NiGHTS doesn't have a specific gender. While most fans picks a gender they see it as, it's still a generally agreed fanon that NiGHTS choose what gender it feels like being. This is opposite of the early days of fandom, where any opinion that wasn't "NiGHTS is male and that's canon!" led to condescending, implications that you weren't a true fan, and/or being banned. There are still a few fans like this, but thankfully they're a minority.
Going with the NiGHTS into Dreams... bit, the character of all the other characters (excepting Reala and NiGHTS itself) is completely based in fanon, to the extent that some people complained when the second game was released, saying that the characters "weren't true to canon." This seems to have been remedied somewhat over time, however characters such as Jackle are still prone to this.
NiGHTS and Reala are still prone to fanon-based characterization, since it was only in JoD they got obvious personalities... and even then not everyone sees it as canon.
It's long been stated by certain Chrono Trigger and Chrono Cross fans that the royal family of Zeal dye their hair blue. This is never stated in the games or by Word of God, though it's often told by fans that someone in Chronopolis says it (they don't) or was mistranslated in the U.S. (it wasn't) or it was in the PS1 remake (it wasn't) or again, that it was left out in the U.S. (it still wasn't). The theory mainly exists to explain why Schala has blond hair in Chrono Cross, because the game never explains why Kid, who is explicitly Schala's clone, is blond, as well as Schala herself in the closing scenes of the game. There are many that understand this to simply be fan theory, but internet legend sometimes elevates this to canon.
There's a truckload of old theories concerning the Mega Man series and its spin-offs; one dealt with the last names of most of the X series characters (Signas Lancaster, Marty Gisbon, Iris Thorne, etc.). The best was "Zero Omega."
Zero killing most/the whole cast of the original series (this has been Jossed). This was popularized by Bob and George.
The DWN Robot Masters living in Wily's fortress in between/during the games. Probably canon for the TV series, but that's not the same continuity.
One of the biggest problems is that early Mega Man (not Rockman) stuff was prone to embellishment, so much that it could be considered its own continuity. That in itself isn't too bad—this happened a lot in the NES era—but many fans aren't too happy with it. If they don't dismiss it all as mistranslations, they claim it's compatible with the original canon material, despite not perfectly overlapping at all, and then embellish further in order to explain certain points or cover plot hole (absolutely not helped by some people considering fan translations of dubious quality or fanfiction as canon, nor by assuming that everything the Japanese fans said was true; that's where those last names came from). While it's not as bad today as it was in the early days of the community, there's still people who think/insist that Doctor Light and Wily being partners is true for all regions, or that Mega Man knows that Proto Man is his brother in the Japanese continuity.
In the Battle Network series, the premise of MegaMan.EXE and Lan Hikari's link has been debated in fanfiction due to its vagueness of detail in the games. Many fan works will include the link as having the two be able to communicate telepathically or control each other's bodies.
In Mass Effect, female Shepard is far more commonly presented as the canonical version of Shepard, despite male Shepard being used in all of the promotional materials and statistics revealing 80% of players choose to play as him.
Due to both male Shepard and female Shepard's individual voice actors being Canadian, an Earthborn-origin Shepard is thus Canadian. Acknowledged in Mass Effect 3 where Shepard can offer to take his/her romance interest out drinking in what's left of Vancouver.
It was common for Garrus Vakarian's unseen and unmentioned mother either dying or divorcing his father before the game took place. Both have been Jossed due to information found in Lair of the Shadow Broker, which revealed that his mother is alive and dealing with the turian equivalent to Parkinson's/Alzheimer's, with his sister taking care of her. It's implied that his mother then died in the time skip between the second and third games.
It's also common for Joker to only be able to walk because of surgery/enhancements from Cerberus. There isn't actually any dialogue to support this. In fact, Joker was able to walk in the first game, he just stayed seated for the entire game because he's the pilot and didn't need to get up.
A controversial one purported by Tali's more devoted fanbase is that she can successfully give birth to Shepard's baby, either normally or with Mordin offering assistance (which would be grossly out of character for him). Never mind the fact that writers forget the protein difference between them would have disastrous results.
Due to a number of well-done fanfics, it's become increasingly likely for Miranda to have relocated Oriana to the Citadel, where she meets and befriendsKolyat.
Due to the official image of Tali being a photoshopped stock photo, fanfic writers still readily embrace the idea that Tali possesses Cute Little Fangs and is known to occasionally purr like a cat.
A particularly popular theory on the ending of the series is that Shepard was actually indoctrinated from the point that s/he got hit with Harbinger's beam, with the final choices being whether or not Shepard successfully fights back or succumbs to the Reapers' influence.
Due to the clunky Mako controls in ME1, some fanfics have Shepard be a bad driver, with the squad have varying amounts of fear to Shepard's driving. This is kinda reinforced by a line Liara says in during the Lair of the Shadow Broker.
Fanfics like to have Prazza be a total idiot with no sense of tact or restraint even though the most we ever see of him is showing very justified distrust of Cerberusnote remember they are a human supremacist terrorist organization that tried to blow up a Quarian ship and ignoring an order from Tali in an effort to reach a quarian before Shepard's team can.
Due to Mordin's popularity, fans tend to think that all salarians speak the same way he does even though we meet plenty of others who both speak more slowly and in longer sentences.
Vanguard seems to be a preferred class for Shepard in fanfics, especially on Spacebattles.
Fans who think about the subject at all usually identify Liara's maternal grandfather as a salarian.
Shepard is commonly presented in fan fiction as being a fan of the Blasto movies. This one died down after Shepard's reaction to making a cameo in Blasto 7.
Making Udina actually competent and helpful is fairly popular.
Knights of the Old Republic: Female Revan stories outnumber the "canonical" male by about a five-to-one margin. KOTOR has several bonuses for a female character anyway; Carth's dialogue tree being largest in-game (only half of it accessible to male players), a second romance option with Juhani, and a third ending where a Dark Side female could choose to sacrifice herself, and David Gaider made the whole thing clear as mud when he showed up on the fan site and submitted a female Revan story.
Apparently this fanbase for female Revans led to the Exile in KOTOR II being declared canonically female.
Another popular fan theory is that Carth Onasi is an untrained Force Sensitive. This is based on the character's uncanny intuition, bizarre luck, and the fact he came from a planet populated by Jedi washouts. It also doesn't hurt that he was able to see and understand a Force Ghost (something only Force Sensitives can do according to the d20 rulebook) and that his son was training as a Sith.
Thanks to one scene between Admiral Tolwyn and Col. Devereaux, in Wing Commander II, it's widely believed by the fandom that the Phase Transit Cannon on the TCS Concordia has a tendency to blow up. All the actual scene says is that it's not safe to fire when at only 60% power, and that from a character known for being strictly "by the book", making it likely that Angel was thinking of technical documentation that errs on the side of caution.
Hobbes' betrayal in Wing Commander III is often said to be because he didn't want his homeworld blown up, but canonically he was a sleeper agent for the Kilrathi, established years prior to the third game. The video clip that explained this was present on the Three DO Interactive Multiplayer and PlayStation ports of the game, but cut from the PC version due to space limitations of PC CDs at the time.
It's often stated that Tauros and Miltank are opposite gender-counterparts of the same mon like the Nidoran line(s) and Volbeat/Illumise, but this has never been stated in the games or the anime. It actually has some basis in gameplay - their stats total the same, they're always found in similar/the same locations outside of Safari Zones, etc. - but, nevertheless, the fact that you can't get Tauros by breeding Miltank holds. The same applies to the Vullaby (female) and Rufflet (male) lines.
A popular theory is that the whole franchise takes place After the End and that Pokemon were created by mutation/genetic engineering
Considering how Pokedex descriptions are usually only one or two sentences long, and are usually flat out ridiculous or exaggerate a single trait, fans often come up with more complex fanon descriptions on the biology, habits, diet and life cycle of various Pokémon species. Even TV Tropes has its own pages dedicated to this.
Also regarding the Pokedex, the absolutely ridiculous nature of many Pokedex entries (such as Alakazam's 5000 IQ) has led to the general assumption that they are written by the ten year-old trainers, who obviously have only a cursory knowledge of science.
Most interpretations of the player characters' personalities are pure speculation. Only a few of them are given canon personalities if they appear as a side character when not chosen. But with the exception of Brendan/May and occasionally Dawn, most of these personalities are ignored. Arguably the most notable is Red—there are hints that he is a Hot-Blooded cutie, but he is more often portrayed as a The Stoic due to his silence during the Johto games (which is more likely a nod to his Heroic Mime status in his own games he starred in rather than a hint of his actual personality).
Eye colors tend to be fanon too, sometimes mistaken for canon despite the sprites. For the Kanto trio Red is typically shown with Red Eyes (or black if it's his canon classic design), Leaf with Green Eyes (or the occasional blue eyes), and Blue with Green Eyes despite the fact all three of them have Brown Eyes in canon. Silver is typically shown to have red eyes, despite him having Gray Eyes in canon; the intro accidentally had him with red eyes and his original Gold and Silver concept art had him with red eyes, but his official art and sprites have him with Gray Eyes.
A good chunk of that is most likely the result of Pokémon Special where each of the main characters have eye colors matching their name; Red has red eyes, Green (known as Blue internationally due to a Dub Name Change) has green eyes, Gold has gold, etc.
Fanon has it that the protagonists and rivals are True Companions. This means that Red, Leaf, and Blue are often depicted as being childhood friends (sometimes Red and Leaf are even twins, which is an sensible theory honestly). Hilbert and Hilda from Pokémon Black and White are depicted as friends, sometimes even siblings, despite the fact they're strangers as of Black and White.
Fanon tends to think of May as the main protagonist of Ruby/Sapphire/Emerald, and Brendan being the Birch kid, partially due to May's role in the anime being the "protagonist" version of herself. There is one exception, though it began before the anime's respective arc was dubbed into English.
Back in the original Red/Blue, The Rival has a Raticate on his team during one of his early battles. When he is next seen, he's at the Pokemon Tower (a memorial where people pay respects to deceased Pokemon), and he no longer has his Raticate. You'd be hard-pressed to find any fan who doesn't believe his Raticate died somewhere between those points, despite it never being said in-game.
HeartGold/SoulSilverconfirms the long-speculated theory thatSilver is Giovanni's son (a connection that's been hinted since FireRed/LeafGreen when one of the scientists on the Sevii Islands notes that "Giovanni's child has red hair"). On top of this, the Gen II remakes also introduced us to Rocket Executive Ariana. Given her apparent age, the fact that she's second in terms of authority out of the four Executives (behind Archer), her idolization of strength, her looks, her name (Ariana is Welsh for "silver"), and the fact that she's the only female Executive period, fan speculation places her as Silver's mother (though the nature of Giovanni and Ariana's relationship is left up to personal interpretation).Just about every corner of the fandom has rolled with this.The ship, in some circles, is known as Silverspawn Shipping, by the way.
A bit crackier in nature (but still mildly popular) is an extension of this theory, claiming that Galactic Executive Mars and Gym Leader Roark (both from Diamond/Pearl/Platinum) are also related to Giovanni, Ariana, and Silver. Mars is placed as Silver's big sister, while Roark is their half-brother through Ariana (remember, Roark already has Bryon as a father).
A good portion of the fandom seems to think Giovanni committed suicide in one of the events for HeartGold and SoulSilver.
Popular fanon has the Striaton Trio being the Shadow Triad. This was later heavily hinted in Pokémon Special but has not been confirmed yet in any media. The games ended up making them separate characters but there's suggestions they were meant to be them.
An alternate piece of fanon is that there are two Shadow Triads. One consisting of the Striaton Trio (BW Triad) and another consisting of some other men (BW2).
An extremely popular fanon revolves around Red. In most fan art - excluding FireRed and LeafGreen fan art—people will draw him as being an older, more bishonen, cleaned-up version of his classic version. This character (nicknamed "Pixiv Red" or "Uber Red") is typically The Stoic and The Silent Bob, and more often then not has red eyes. He's received immense Internet Backdraft due to his differences from Red's canon depictions and the fact he's overly popular to the point where you can barely find fan art for Red's canon designs... But is still the most common depiction of Red in fan works.
Fanon has the Black/White protagonists at 16, occasionally 15. Nowhere has their age been stated so far. All that's been said is that they're older than previous protagonists, who have a Vague Age onto themselves.
Other protagonists are typically stated to be ten. This may be true for their counterparts in other media but in the games they have no stated age. The only one with an age is Red, who's eleven in his games (and thus fourteen in the Johto ones).
Similar to the above Ariana is Silver's mother theory, some B/W fans have been trying to discern a connection between N, Anthea, and Concordia, particularly the school of thought that one of the two is N's mother (Concordia is the more common choice due to Theme Naming with N, whose full name is Natural Harmonia Gropius; Concordia is the Roman goddess of harmony, Harmonia is her Greek counterpart). This has been shot down by B/W2, as the two women reveal that all of three of them were orphans taken in by Ghetsis, thus making Anthea and Concordia N's adoptive/foster sisters.
Brendan having white hair was extremely common fanon until Word of God confirmed a knit hat. Fans still like to cling onto it though, suggesting he has Multicolored Hair.
There's a widespread theory of Gens taking place at the same time, driven by the ability to trade between Gen III and IV games and the I and II remakes. IE, Gens I and III and II and IV take place at the same time. However, the time travel factor that also exists in places makes this unverifiable.
Considering that, among other hints, D/P begins with the player character watching a newcast about the Red Gyarados from G/S/C (or, more likely, HG/SS), this is much less Fanon than one would think. Gen V, obviously, occurs later in the timeline than Gen I/III and Gen II/IV.
None of the player-named heroes in the Suikoden games actually have canonical names, but fans often use the names that were given in the Japanese novelizations of each title (i.e.: the hero in the first Suikoden is known as Tir McDohl).
Plenty of background information for the earlier Tekken games which is considered canon by fans come from two fan-made story guides which implemented "facts" from the non-canonical OVA and their own fanfic ideas to clear out perceived plotholes due to early game's bios being only on Japanese guides/websites. And that's not counting random changes to translated profiles. Among the most noteworthy:
Lei Wulong and Bruce Irvin being former police partners. Their official bios for T2 have Bruce as an unrelated Muay Thai champion being targeted by a local mafia, and Lei's actual nameless partner getting involved in a fight with the killer on the same plane Bruce was. Bruce has never been a police at all, and his relation with Lei in-game is just because he was involved in the accident and is Kazuya's bodyguard.
Ganryu having amassed a fortune through gambling/illegal dealings, and his money being stolen by Yoshimitsu. Ganryu's T1 profile states he was only a very disrespectful sumo, which cost him his Yokozuna promotion. There's no mention of any fortune in canon, and the money Yoshimitsu gets in his ending is officially stated to be from the sacking of the Mishima's Vault.
Coming from the above, most sites ignore Yoshimitsu's ending as the reason Marshall Law obtained money without winning the tournament, and claims instead he got third place. Besides that never appearing in any profile, a Tekken 3 official guide states Yoshimitsu's ending as the actual source of Marshall's money.
Nina and Anna blaming each other for their father's death. Anna's profile in T1 clearly states Anna hates Nina because their father prefered her, since she embraced the assassin career while Anna preferred a normal lifestyle, a decision her father never approved of.
Wait. Don't their T2 bios state that their father died mysteriously and both blame the other for his death? Also, what about their T2 ending at his grave!?
Armor King (the 1st) being a Mexican super wrestler from a mystical "Jaguarandi" tribe. Armor King's country is Unknown, no such tribe is mentioned in any source, and he's been never stated to be anything more than a "regular" wrestler.
Christie's grandfather being called Ho Chi Myong and Kazuya's mother being Kazume, both originating from a fan-made roster for a prequel fanfic. While Kazume seems to be an attempted romanization of her official name (??, Kazumi), the author explicitly said to have made Ho Chi Myong up. On the same vein, Kazumi's alleged Death by Childbirth is exclusive to the OVA, with official sources only stating her death was "accelerated by Heihachi's indifference."
The Deal with the Devil Kazuya did to survive being thrown off a cliff, only ever mentioned in the OVA. According to Devil's profile in T2, Kazuya wasn't even aware of his existence, and the fall's survival is credited to the Mishima lineage's Nigh-Invulnerability. On this subject, Angel's profile never mentions anything about being "Kazuya's good side" and instead claims she and Devil are "the two sides of the same coin."
Heavy/Medic is one of the more popular pairings due to some of the Heavy's lines in-game.
Despite Word of God from Valve, some fans continue to believe that the Medic is an ex-Nazi (which would make the above example very confusing). Others belive he's Jewish.
A minor fanon is Scout's dogtags being a memento of his father or one of his brothers.
The Engineer either cut off his hand (most likely given the description) or according to some fanon always had one, he just hid it under his glove and replaced it with the gunslinger when he found the blueprints.
Excellen seems to attract a lot of these. In the Endless FrontierGaiden Game, Lemon's name is mistranslated via Woolseyism into "Raymond", despite it canonically being the former. However, fans have adopted "Raymond Browning" as the name of her father, whom she mentions in Original Generation 2, but is never seen.
Animal Crossing fans tend to refer to Timmy and Tommy, the two Single-Minded Twins who come to work for Tom Nook, as Nook's "nephews." In-game, though, they're given no relation to him other than that. Fandom simply extrapolated based on the commonality of Chaste Toons.
I think Nook says they're his nephews in the French version...
If we're going by translations, then it's possible that it comes from the Japanese version and was mutated from 'ojisan' which is roughly translated to 'uncle' but is often a way of hailing a man who's older than you, whom you know (it's casual and, IIRC, childish— think of a little kid calling a friend of his/her mom's "auntie"). That's the way my teacher taught us, at least, so I may be wrong on more than one level.
In The World Ends with You, it is commonly assumed that Rhyme's entry fee was her dreams/ambitions, although it was only implied. It's also fairly agreed on that the main reason Shiki was in Eri's body for Another Day was that the artists were too lazy to draw new sprites for her. Joshua leans on the fourth wall in support of this theory.
The concept of a "Music of Shibuya" shows up in nearly any fanfic that focuses on the roles of Composer and/or Conductor. The word actually never came up in the game. Neku is also often given a sketchbook and a talent for drawing, even though all we actually know of his art sensibility is that he likes CAT - who is a tag artist, but also a designer and makes... ads about... stuff.
An incriminating letter found in King's Quest VI: Heir Today, Gone Tomorrow was meant to be "merely" a document implicating the game's Big Bad in the events of the fifth game. However, the way the letter was worded implied a much wider conspiracy at work. The fans started speculating about the Society of the Black Cloak, and have pretty much run with the idea that most (and possibly all), the enemies of Daventry's royal family belong to its ranks. The Fan Remake of King's Quest II: Romancing The Throne uses this assumption with the character of The Father, and the Fan Sequel has also introduced a member of the Black Cloak Society as the family's nemesis.
Speaking of, the AGD Interactive games are entirely fan-made works, and the Fan Remake of KQ2 wildly contradicts the original in several places, but has enough of a following to take on fanon status.
Another, more contested, bit of fanon states that Rosella will eventually marry Edgar and move to Etheria, leaving Graham to appoint Mask of Eternity's Connor MacLir as heir, the way Edward the Benevolent did for him. The controversy stems from Mask of Eternity's dubious standing in the fandom.
In Persona 4, the romantic subtext between Chie and Yukiko is so damn evident and "in your face" that it almost feels like Anvilicious. Because of this, many fics portray them as a couple, even when they are not the focus of the story.
Roughly everyone's sexuality is up to fanon. Yosuke and Teddie flirt any girl they see but still share heavy Ho Yay moments with the protagonist. Kanji tries too hard to prove he is straight and still has many gay moments. While Naoto is a possible love interest, she isn't interested in anyone and everyone refers too her with male japanese pronouns. Some believe Everyone Is Gay, others believe Everyone Is Bi.
There are exactly two moments when Naoto's bust is brought into question; one vague hospital scene where she's embarrassed to have her measurements read, and again during the Hot Springs Episode. Fanon decided to take this ball and run with it straight outta the stadium, and the grand bulk of her fanart depicts her with downright tremendous assets, easily surpassing D-cups. Meanwhile in Canon, the hot springs character cut-out and the anime of the game show only a slight elevation, nothing more than a modest B-cup. However, in Persona 4 Arena Akihiko states that she's keeping a lot hidden.
F-Zero is subjected to copious amounts of fanon, due in part to the (now defunct) North American website for F-Zero X, in which it included many character elements that would later be adopted by fans (the big one being Douglas Jay as Captain Falcon's name) Most of, if not all of these elements were roundly Jossed when F-Zero GX came out several years later and there was a more unified translation. But while it could be considered fanon in the basic sense of the word, a lot of the NA F-Zero X information is still treated like it's official canon.
And while GP Legend is considered an Alternate Continuity series, a popular piece of fanon is that anime-only Lisa Brilliant (the wife of Samurai Goroh) is the mother of game-only Dai Goroh (Samurai Goroh's son, making his debut in F-Zero GX/AX).
Though there's not much evidence to support it other than somewhat similar appearances (and Etna's commitment to fanservice), many Disgaea fans have it that Etna, Hanako and Raspberyl are all adolescent succubi.
Another fan theory involves Sheeva from 3, a member of the Shokan race much like Goro and Kintaro. Whereas Kintaro was explicitly said to be Goro's cousin, Sheeva's relation to the Shokan prince (if any, besides 9 stating that they hail from the same lineage of Shokan, the Draco tribe) has never been disclosed. Speculation commonly places her as either one of Goro's relatives (usually his sister or cousin) or his wife (of whom Goro is mentioned to have seven, according to the first game's official comic and instruction manual).
The Sims 2 has some fanon despite being a Wide Open Sandbox game. For example, the townie Meadow Thayer is often used to give a Teen their first kiss (because she's one of the few female teenage townies), and there are certain sims that are often played as gay like Frances Worhington or Nervous Subject.
There's a little bit of joke fanon that the muffins a child make in 3 have meat in them, as vegetarian Sims get sick from eating them.
With the revelation in Portal 2 that GLaDOS is a brain uploaded human, it's become widely accepted that the personality cores were created the same way.
Further, Wheatley's theorized human self is almost universally described as resembling StephenMerchant.
Virtually everybody assumes that Chell is the daughter of Aperture's founder Cave Johnson and his secretary Caroline. There is evidence to suggest she was the daughter of someone at Aperture (her apparent signature appears on a children's science project in the 'Bring Your Daughter to Work Day' display) and the assumption is sort of understandable since Cave and Caroline are the only other human characters named in-game and GLaDOS, who has Caroline's mind inside her, is obsessed with Chell to an almost mother-like degree, but nowhere does it imply she was anything near as important as the daughter of the founder. Plus, Cave Johnson died in the early 1980s and was already old man at that point (He looked like this circa 1943). In the first game, Chell looks like she could maybe be a young-looking fortysomething at oldest, and in the higher-quality graphics of the second she doesn't look a day over 30. Cave could have invented something to keep his daughter young or himself and Caroline fertile, and he's crazy enough to force people to spend years in stasis or something, but you still have to be really trying to interpret him as Chell's father to make it work.
There is also the fact that the Prima Donna Turret, who is most likely controlled by GLaDOS, explicitly calls Chell her daughter in one of the ending songs (in Italian). Whether that's metaphorical or not is up to you.
There is also a common belief that Chell has no memory of anything before Portal 1 based purely on the fact that we are given no information on her backstory, and possibly the fact that she seemed to not know GLaDOS was evil.
Widespread Dragon Age II fanon has it that Merrill is a virgin (she usually fails to understand innuendo) and Anders is claustrophobic due to having spent a year locked in solitary confinement (he does comment in a frightened voice "I really need to stay out of the Deep Roads" if clicked there, though there might be other reasons for that). It's also generally agreed that Danarius sexually abused Fenris when he was a slave, though that's a case of Writer Induced Fanon which was intentionally implied. Other bits of fanon are that Fenris is an alcoholic and that Anders isn't that character's real name but rather a reference to his (supposed) nationality; in the latter case, he's usually given something German or Polish as his "real" name, due to Fantasy Counterpart Culture cues in the game world.
Anders being a nickname because he's from the Anderfells isn't fanon, it's canon. Check his Codex page.
The writers have confirmed that Fenris was sexually abused as a slave. Squick...
Harvest Moon fanon has most male protagonists being called "Jack" despite the fact each design has its own name, and none of them are called "Jack". The female protagonist in Another Wonderful Life is officially "Pony" but fans prefer "Jill".
In Harvest Moon 64 it's implied Gotz is abusive to at least Sasha but it's never confirmed.
Certain couples are more or less so widely shipped they're fanon. Celia-Mark and Pony-Marlin come to mind.
It seemed to be agreed upon in the Dawn of War fandom that the Imperial Guard won the Kaurava campaign in Soulstorm even though the sequels never really revealed who won the conflict, only that the Space Marines lost.
May fans believe that Sly Cooper's dad's name is Connor Copper.
Spice in Spore is, from a gameplay perspective, merely a commodity to be bought and sold at a profit; while it's not elaborated on much, the descriptions suggest that it is seasoning for food (also floor polish). However, the general consensus among fans is that spice is actually drugs, due to how the word is used in Dune and the Star Wars Expanded Universe (and possibly some other Sci-Fi franchises as well). User-made levels for Spore Galactic Adventures have shown examples of spice dealers, spice smugglers, spice junkies, and even a campaign to ban spice.
Quite a few Halo fans consider Red vs. Blue to be a sort of "unofficial canon". Basically, they acknowledge that it isn't really canon, but still consider it to be just as much a part of the Halo universe as the actual games.
It's unknown what the bond between the Ice Climbers is, but the most common beliefs are they're siblings or they're lovers. Sometimes they're both. Likewise their ages are ambiguous but fans typically have them as children around 10 - 15.