Fanon/Western Animation

Examples of about  include:

Avatar: The Last Airbender
Avatar: The Last Airbender, due to largely its implied and All There in the Manual worldbuilding, has a lot of this, along with character interpretation.
 * A relatively less likely to be contested one is that Jet's Freedom Fighters all go by nicknames assigned by their leader Jet.
 * Some people still insist that bending ability and talent is a case of Lamarck Was Right and/or Superpowerful Genetics. This is despite the fact that Katara and Toph are the only benders in their families, there being a set of twins where only one was a bender, it being said that people first learned bending from non-human sources, and Word of God speaking to the contrary several times, saying that bending manifests due to a mix of genetics, spirituality, and training.
 * Technically, while Toph's parents are never shown earthbending, that doesn't mean that they aren't earthbenders. On the other hand, Toph learned earthbending from badgermoles anyway. In fact, the Original earthbending was learned from badgermoles, just as dragons taught firebending, air bison taught airbending, and the Moon inspired waterbending. Unless those people are somehow part animal (and part-moon), that would indicate it's not genetic. Yue, at least, demonstrates that someone can be, if not genetically, then spiritually part moon, and yet she's still not a waterbender.
 * It is widely accepted Fanon (for whatever reason) that Azula is a flaming dyke. She is show attempting, and failing, at heterosexual dating in-canon. Both of her "girlfriends", Mai and Ty Lee, are interested in boys. For some reason, everyone insists she's 100% lesbian.(Pun intended.) She's also a serial rapist, if you believe the fanon. Her victims include Mai, Ty Lee, Suki, Sokka and Zuko.
 * Another Azula fan-theory getting passed around in some circles, possibly as a twisted spinoff of the above fanon, is that she has a strap-on that she calls "The Dragon Down South" (with which the aforementioned raping is done. This includes the men). Some fanworks go further and claim it's not really a strap-on...
 * When first introduced Toph and Aang were 12, Azula, Ty Lee, and Katara were 14, Sokka, Suki, and Mai were 15, and Zuko was 16, and by the end of the series about one year had passed. Any other exact ages are fanon, especially the insanity of how someone as Bishonen as Ozai is Iroh's brother. There are actually siblings that are relatively close in age, yet look at least one generation apart in real life. Maybe Ozai is very particular about his appearance and Iroh just doesn't care? The answer is implied, but never stated, in canon. Ozai lived in luxury with his children. Iroh lived in warzones, where he lost his only son. Or more likely, their parents had Ozai later in life. It would explain the lack of closeness between him and Iroh as well.
 * A popular notion in fanfiction is that citizens of the Fire Nation worship the Sun Spirit as a god and call it Agni. Several factors contribute to this bit of Fanon: 1) As waterbenders are empowered by the moon, and the Northern Water Tribe worships the Moon Spirit, so firebenders are empowered by the sun, therefore it seems logical that the Fire Nation would worship a Sun Spirit. 2) Agni is the name of the god of fire in Hindu mythology, and the Fire Nation has a custom of firebending duels called "Agni-Kai." 3) You have to give Fire Nation characters something to say when they feel like swearing. This was later clarified. The original firebenders the Sun Warriors worshipped the sun as the source of firebending, but the Fire Nation forgot about the sun, and instead drew on personal rage and drive to fuel their firebending. No mention of a god named Agni has ever come up, but that's to be expected since the Avatarverse has spirits, but no mention of gods, and for the most part, mortals don't know the names of spirits either.
 * Zuko's season-one hairdo is called a "phoenix tail," apparently. Maybe because "ponytail" sounded too fun and perky. It does seem likely, as Sokka's ponytail is properly called a "warrior's wolf tail." On the other hand, the scene in which this is revealed makes it clear that the word "ponytail" does exist in their world.
 * Despite no one in the show has ever saying, "Oh, Spirits!" (or any variation thereupon) to express frustration, it's extremely common in fanfiction.
 * More and more fanfic writers are portraying Ozai as a coffee aficionado, in contrast to Iroh's famous love of tea.
 * Too many fanfic writers seem to believe that Toph only refers to people by nicknames. In actuality, most of her nicknames ('Snoozles', 'Madame Fussy Britches' and 'Sweetness' to name a few) were just one-timers. 'Twinkletoes' is one nickname she actually stuck with, but if you believe the fanfic writers, this would be the only name that Toph ever knows Aang by. Popular Zuko nicknames seem to include 'Sparky' and 'Hothead'.
 * For a mockery of all this, see The Ember Island Players.
 * Shippers from The Legend of Korra were quick to create the very common fanon that Asami likes Korra, not Mako. Some have even gone far enough to say she smashed into him with the purpose to meet Korra (though that's more typically Played for Laughs).
 * Ascended Fanon or not, the finale of LoK in December 2014 indicated that Korra and Asami were in love. And just to make sure it was very clear, both Michael Dante DiMartino and Bryan Konietzko took to the Internet a few days after the broadcast to confirm that Korra-Asami is canon.

My Little Pony

 * The gray pegasus extra in My Little Pony: Friendship Is Magic. Spotted with wonky eyes in a very brief shot, she was quickly embraced by the show's adult viewers as "Derpy Hooves" and cast by one fanfic writer as a mail carrier. There are varying interpretations of her personality, but her name and occupation are generally agreed on.
 * Frequently, Derpy has a daughter named Dinky Hooves, a purple unicorn with a blonde mane that first appeared in "Winter Wrap Up".
 * Occasionally her daughter will be the child of either Pokey Pierce, his Palette Swap Ponet (who is also a purple unicorn with a blonde mane), or another background pony. If shipped with Doctor Whoof, she'll be the adopted daughter of his.
 * Derpy has been confirmed for the postal service, and in "The Last Roundup," Rainbow Dash addressed her by name.
 * According to this leaked storyboard, the makers of the show consider Derpy to be her name.
 * Derpy is frequently Doctor Whoof's companion; if not, Twilight Sparkle or Colgate (Romana) takes that role.
 * Since "Winter Wrap Up" and some Word of God saying they might use Derpy's character design for a named character, many fans have used Ditzy Doo as Derpy's "real" name, usually the ones who play her up as being smarter than she looks.
 * Also, the widespread view that Rainbow Dash, the athletic tomboy with rainbow hair, is a lesbian.
 * An Inversion is also somewhat popular, that she's the only one out of her friends (besides Spike) that is Straight. Also for some reason, her G3 version is often thought of as a Lipstick Lesbian but Firefly is seen as Camp Straight.
 * For ponies with a two part name, the second half is often treated as a surname.
 * Sort of confirmed in the episode "Cutie Mark Chronicles". Pinkie Pie's full name (as said by her parents) is "Pinkamena Diane Pie". Twilight is also referred to as "Miss Sparkle" in the same episode.
 * And her family has been given nicknames: Inkie, Blinkie, Clyde and Sue.
 * Also there is Rainbow Danger Dash.
 * Also popular are names for background characters that appeared in as little as one scene in one episode. Sometimes they're named for their cutie marks (Lyra and Bon-Bon for their lyre mark and wrapped candy mark, respectively). Sometimes the name is decided by the fans in a somewhat-official poll (the unicorn DJ in "Suited For Success" is named Vinyl Scratch, with a stage name of DJ PON-3). And sometimes, the name just comes out of nowhere; the mustachioed sea serpent that appeared in the pilot episode is now known as Steven Magnet due to YouTube's hilariously bad speech-to-text translator.
 * Bon-Bon is named for the G1 pony with the same mark and similar colors.
 * Bonbon will occasionally be a Jerkass due to the way she acts in her few speaking roles.
 * Every time Bonbon had a line she spoke with a different voice. This has led to the believe that Bonbon is a voice actress or (after Season 2 final aired) a Changeling.
 * Lyra having an obsession with humans due to her slouching on a bench like a human being in the background in one episode. Many fan takes on this have been seen, from mimicking human behavior, to her obsession with attaining hands, to her dream of becoming a human being herself.
 * Lyra and Bonbon are the One True Pairing of the fandom. No matter what, they're always a couple. Occasionally they'll have a child together, and occasionally Colgate will get in the way of their romance (though she's commonly shipped with Berry Punch), but typically they're a couple.
 * When the cast is "humanized" in fanart, Twilight is often given a brown-skinned ethnicity, most often African-American or Indian (probably because her purple color makes her the darkest pony of the mane six ), and seems to really, really like lavender sweatervests. No one knows why, though the second can be attributed to sweatervests being associated with intelligent and/or academic characters. Similarly, Applejack wears cowboy-ish clothing, Rarity dresses stylishly and lady-like (typically she wears fashion from The Roaring Twenties), and Rainbow Dash dresses tomboishly, often in sweatshirts.
 * The fans even have a punny name for when Human!Twilight is drawn as a brown-skinned ethnicity: Thai-light Sparkle.
 * Human!Twilight's typically drawn in a school uniform, and even in casual wear she's prone to sweater vests. Human!Fluttershy is almost always depicted as wearing sweaters, with the occasional summer dress as an exception. Human!Rainbow Dash is typically a Pettanko, Human!Celestia often has rather tanned skin (being a sun goddess and all), with Luna being very pale. Human!Pinkie is occasionally Latina, while it's somewhat common to draw Rarity as either extremely pale or Black. Pinkie almost always wears either a pink t-shirt with her cutie mark on it and jeans, or a poofy dress.
 * Also it's all but mandatory to draw a fully clothed Human!Gilda in a bomber jacket.
 * Asian is another popular choice for human!Rarity.
 * Fluttershy is occasionally depicted as a Muslim, with the wrap instead of her distinctively impractical hairstyle.
 * Fluttershy as being a MtF Transsexual is another popular one, derived from her enchantment-enduced time as 'Flutterguy'.
 * Another common depiction for Fluttershy is giving her huge breasts; this is given the Fan Nickname "Hootershy".
 * Flying for Pegasi is often changed into running, though occasionally you'll see it made into flying with jet planes.
 * In some Fan Fics, especially in the Shipping Fics, lesbian ponies are called filly foolers while gays are colt cuddlers. Jackmare (a jack is a male donkey) and gelding (a castrated horse) are less often used as the equivalent of dyke and fag.
 * Unicorn horns are usually portrayed as erogenous zones (especially in fanart), most likely due to their phallic appearance.
 * Similar, but unshorn fetlocks are kinky or sexual.
 * That came from a piece of fanart that had Luna (who was imprisoned in the moon for the last thousand years) shocked to see colts walking around with unshorn fetlocks, and generally treating it much the way a Victorian transported to modern America would react to (gasp!) bare legs.
 * Pegasi wings are also treated as erogenous zones. Mostly comes up in Twilight Sparkle/Rainbow Dash and Pinkie Pie/Rainbow Dash drawings.
 * Some say Rainbow Dash's middle name is Miriam.
 * Similarly, some say Vinyl Scratch's middle name is Jennifer.
 * Firefly, the G1 pony Rainbow Dash is based off, is often thought to be her mom (or at least a close relative). Less common, but Posey is often Fluttershy's mom.
 * Fanon has G1 taking place in the 80s of the Ponyverse, or at least the characters from G1 existing in G4. The most common to appear are Surprise, Twilight, Posey, Sparkler, and Firefly. Surprise is typically a relative of Pinkie, though recently her being a Wonderbolt has been popular due to the fact one of the mares has her coloring. Twilight is typically Twilight Sparkle's mom, which may be canon. Recently Twilight's dad has been referred to as "Nightlight" a lot, since his coloring is so similar to a G1 mare by the same name and it goes with a theme naming if his wife and daughter are called "Twilight".
 * Applejack's trademark cowboy hat is often stated in fanon to be a family heirloom from her father, who has yet to appear on the show, and she's thought to be very protective of it.
 * Some fans have joked that Rarity's sensitivity to being called a mule means she was raised by them. On a more Squick-ish part of Fanon, it's a popular belief that Applebloom is Applejack's and Mac's child, and that Sweetie Belle is Rarity's illegitimate child with someone.
 * Since the airing of "Sisterhooves Social", it's been revealed that Rarity and Sweetie Belle were not raised by mules, and that not only is Sweetie Belle NOT Rarity's child, she lives with hers and Rarity's parents!
 * That doesn't totally rule out the "Sweetie Belle is Rarity's illegitimate child" bit, but it's unlikely The Hub are ever going to go there.
 * Rarity and Cheerilee are often depicted as being the same age, generally in their mid-thirties, due to Cheerilee apparently being in Rarity's fillyhood flashback and Cheerilee mentioning The Eighties.
 * Another popular bit of fanon is that the G3/G3.5 Cheerilee and the G4 Cheerilee are the same character, with the G4 Cheerilee reminiscing about her "college days" as an childhood education/development major (the G3/3.5 theme song mentions her reading stories to other ponies).
 * Celestia having a pink mane as a filly is popular Fanon, due to the intro depicting her with pink hair. Another popular fanon is Luna calling Celestia "Celly" or "Tia".
 * Vinyl Scratch, the DJ Pony, has red eyes in fanon. Which was Jossed in the Season Finale, where she has Purple Eyes.
 * Luna being introverted.
 * Big Macintosh often has a Gag Penis, which sort of makes sense if you know horse anatomy. Some elements of fanon also include him being called "Lil' Macintosh" as a colt and him being called "Big Mac" as a nickname (he's never been called it due to potential lawsuits with Mcdonalds).
 * That last part is Jossed in Hearts and Hooves Day. Cheerilee refers to him as "Big Mac" the first time the CMC set them up.
 * The Mane Cast often goes by specific names when their genders are swapped, named after a fanfic. Names like "Barbara" for Spike and "Elusive" for Rarity.
 * Some of the toy Ponies, often dubbed "Hasbro's recolors" due to the fact that most of the official artwork is recolored versions of stock artwork for the Mane Cast, are beginning to have Fanon personalities. Firecracker Burst is often known as a Yandere or Genki Girl Pyromaniac. Dewdrop Dazzle is typically a Parody Sue who is obsessed with friendship. Minty typically has her G3 personality, occasionally her G1 personality, often mixed with a dash of Serious Business and Mundane Made Awesome (or an enhanced love for socks); she's typically an old friend of Pinkie. Cupcake (a G1 pony who's been in all the gens) is frequently either the polar-opposite of Pinkie Pie (who may or may not be Yandere due to the Hilarious in Hindsight that pops up due to the Cupcakes fanfic), or a companion to Pinkie due to their love of cupcakes.
 * A rather old piece of fanon that spreads along all series in My Little Pony is that almost all ponies are gay or bisexual, especially the mares. Common duos are Fizzy/Wind Whistler, Glory/Applejack/Firefly and Minty/Pinkie Pie though anyone goes with anyone.
 * Nightlight and Sunlight being siblings, or at least related, is popular. They often have a Sibling Yin-Yang comparable to Fanon Celestia and Luna.
 * Lauren Faust, the main creator of the series, drew herself as a pony, namely an alicorn. Alicorn Original Characters or self-inserts are greatly discouraged due to them almost always being Mary-Sues, but since Lauren is the creator, she deserves to have an alicorn OC. A few artists have even gone on to say that she is Celestia and Luna's mother in-universe. One comic names her alicorn "Tau Sunflare".
 * Speaking of which, the term "alicorn" is near-universally applied to describe Celestia, Luna and original winged unicorn characters, even though that might not be correct usage of the word.
 * There's a pony dubbed "Berry Punch" by fans thought to be an alcoholic (though that has a slight Word of God on its side). She originally went by "Over-Protective Parent Pony" due to a scene where she pulled her filly into her house, when Zecora went near, so despite being an alcoholic she's seen as a good parent. Her daughter is called either "Ruby Pinch" or "Berry Pinch" depending on whom you ask. Berry's occasionally shipped with another pony dubbed "Colgate", though not nearly as much as other Fanon duos.
 * One of the background ponies, dubbed "Wind Whistler" due to her resemblance with the G1 pony, is often depicted as an attention horse.
 * It's become common in the fandom to have Discord be the reason there are so few alicorns, among other things. Another quite common one is that Discord's brutal Break the Cutie on Twilight and resulting mental anguish were the cause of her mental breakdown in "Lesson Zero".
 * Two background ponies, one called "Pokey Pierce" by fans and the other with the canon name "Caramel", are often considered gay. Though occasionally Caramel will be paired with Applejack or Twilight, and Pokey with Pinkie.
 * It's not uncommon to see humans depicted as fictional or mythological beings in Equestria, and occasionally G3, similar to how most people view pegasi or unicorns.
 * While there've ever only been two griffons to show up in the show (Gilda and Gustav Le Grand) and their origins are unknown, it's common fanon that there's an entire Griffon nation that rivals Equestria and wars have been fought (and perhaps still being fought off-screen) between the two countries.
 * Princess Celestia, aka Trollestia or Molestia, is behind everything. (Except Discord.) Despite her godlike power, she is largely hands-off for most of the events in the series, but just about any unusual negative event where the Mane Cast learns a lesson about friendship is laid at her feet by some fan or another. Much more on the relevant page.
 * For that matter, Celestia—and by extension Luna—even having 'godlike' power or any sort of divine status in the first place (because apparently even in the magical land of talking cartoon ponies only bona fide deities are somehow allowed to be able to move the sun and the moon). Pony religion, if it exists, has yet to make a distinct appearance on the show, and inasmuch as fair comparisons are even possible the princesses never seem to display magic quite beyond that of suitably powerful non-winged unicorns. Hasn't kept the fandom from firmly latching onto notions of their 'cosmic' power level or the idea that they aren't even ponies but some higher form of life in equine shape and running away with those ever since...
 * Keeping in the theme of Furry Reminder that makes occasional appearances in Friendship Is Magic, a popular bit of fanon is that ponies still do occasionally graze. That is, walk outside and eat the grass right from the ground. Most ponies only do this as a last resort or in emergency situations, since this is similar to a person on Earth digging through garbage or foraging in a forest.
 * However, it isn't unusual to have whole lawns of specific kinds of grasses and plants planted specifically for grazing. Especially if it's a savored variety.
 * A bit of fanon about Queen Chrysalis is that she is not only the Changeling Queen, she is also the central point of a Changeling Hive Mind. Each Changeling has two consciousnesses: The primary consciousness serves as a direct mental link to all other Changelings, including Queen Chrysalis. The secondary consciousness is (mostly) the Changeling's own, and allows each Changeling to assume different disguises as each sees fit. Unfortunately, there are thousands of Changelings, so each individual is somewhat simple-minded, and only seem to be effective when fighting en masse (i.e.: Zerg Rush)
 * It's also popular to think that Changelings are Equestria's version of the Zerg.
 * There's also the theory that the Changelings are the twisted of the flutter ponies.
 * Any Future Fic that stars the CMC or any of the other foals in the series almost always have them in the same occupations. Though, the whole Cutie Mark thing makes them much more plausible than some other forms of Fanon.
 * Applebloom becomes a handy-pony.
 * Sweetie Belle becomes a singer.
 * Scootaloo becomes a dancer or stunt-mare.
 * Twist becomes a candy maker.
 * Snails becomes a scientist, usually an entomologist.
 * Snips becomes a barber or an apprentice tailor to Rarity.
 * Pipsqueak becomes an explorer or a deckhand on a airship.
 * Silver Spoon and Diamond Tiara usually become business mares.
 * In a similar vein, the Adorkable Twist, Snips, and Snails almost always grow into fine-looking adults.
 * Several possible explanations have been proposed for why Scootaloo still doesn't seem to be able to fly. Even Fluttershy had awkwardly passed the occasional flight exam when she was Scootaloo's age. One explanation is that is starting to gain steam is that she's physically disabled. This translates into human!Scootaloo having a prosthetic leg, such as here, and this fanfiction.

Transformers

 * Transformers fandom has surprisingly little Fanon, and most of it is pretty minor, but there are examples.
 * The group-name "Seekers" for Starscream and other Decepticon jets of the same general build was fanon and later used in official sources.
 * The Minibots were never officially referred to as such. The toys were sold as "mini vehicles".
 * Different characters in different parts of the Transformers multiverse tend to be given the same names and similar designs; for example, G1 Red Alert and Armada Red Alert or G1 Wheeljack and Energon Downshift, yet these secondary characters are generally not regarded as the "same" person. However, some fans believe that each Optimus Prime and Megatron (with the exception of Beast Wars Megatron who was a Legacy Character in canon) are Alternate Universe versions of the same two basic people, while others think each Optimus and Megs are different, cosmically unrelated individuals, who just happens to coincidentally share the same name and role as all the others.
 * You find quite a lot of fanon if you read enough Fanfic.
 * Starscream is either a helpless victim of Megatron's domestic abuse, or a cunning, invincible Badass. Sometimes both.
 * Because Starscream has an immortal spark, he is actually a god.
 * There are so many fanfics where emotionless, monotone Soundwave is portrayed as a loving and caring father to his cassettes. May now be slightly less fanon - in Transformers: War for Cybertron, he.
 * All the Seekers share a kinship simply because they look exactly alike except for their paintjobs. All Seekers exist in Trines and share a deep spiritual bond (sometimes sexual, sometimes familiar) with their Wingmates. The same is often applied to Gestalt teams like the Aerialbots or the Constructicons.
 * Galvatron and Megatron are not the same mech. Megatron is still floating in space somewhere, despite the fact that we clearly see Unicron upgrading Megatron's body in The Movie.
 * Hot Rod was part of a conspiracy with the Decepticons to kill Optimus Prime. This is why he jumped in front of Megatron during The Movie, only to be taken hostage so Prime couldn't shoot back.
 * Several fanfics depict Swoop of the Dinobots training to be a medic, even though he never showed such an interest in the cartoon.
 * Seeker wings are extremely...sensitive. This also applies to 'doorwings', aka car doors that stick out from the back of certain Autobots in robot form, and any wires hidden all that armor.
 * In Beast Wars, Rampage is the son of Starscream. As in biological son, not spiritual son.
 * Beast Wars' Rampage is not, in fact, a psychopath. He's simply misunderstood and depressed.
 * Perceptor is actually the estranged and abused son of Megatron.
 * The Autobots love to party and will have them constantly.
 * It took us this long to get to Cybertronian courtship and reproduction? Transformers have two ways to reproduce amongst themselves. The Allspark, or "spark-bonding." In Cybertronian "marriage" Transformers enter into a symbiosis, merging their sparks together, becoming one being in one body. Also, when two sparks merge this causes an Overload of the two sparks and creates a third spark. Baby Transformers are known as sparklings. Depending on the writer if male bots can reproduce, or just females. And why are females so rare? Megatron killed them all in a fit of madness and preemptive elimination of the hypotenuse. This particular bit of fanon is contradictory to the canon- that they reproduce by manually building a new transformer (or protoform in the case of Transformers Animated), and the spark comes from the local Vector Sigma node/The Allspark/The Creation Matrix. The most romantic bit that can possibly occur is maybe hands touching when constructing the new chassis. This MacGuffin-based-reproduction-only is actually a major series-defining plot point in at least two continuities, and has been the driving force of storylines or episodes in several others. There was even a storyline in the comics where attempts at reproduction on their own led to descendants being increasingly separated from Primus, and increasingly machine-like. There was a Beast Wars episode where Blackaracnia had a dream where she "spark-shared" with Silverbolt, though, so there is a semi-canonical basis for the sex, even if not for the reproduction.
 * Might be slightly less fanon now that the live-actions movies have been released - after all, the baby cybertronians in Revenge of the Fallen have to come from somewhere, even if they do hatch from pods. Also, whenever sparklings do appear, the Seekers are extremely protective of them, which is said to be true for all Seekers (who are portrayed as a sort of sub-species of Cybertronians).
 * A more general case is transplanting traits from one incarnation of a character to another (for example, Animated Shockwave being a Mad Scientist like his G1 incarnation.)
 * Possibly justified since it's usually G1, their personalities are rather flat, so fanon gave them new ones. These ones you're most likely to find in any fic -and it's gotten to the point where the characters seems odd without them.
 * Ratchet being an easily annoyed mech who can work miracles, throws wrenches at everybody that annoys him, and, this can vary, a party animal. He also makes really good highgrade. Also, he worked as a stripper to pay his way through medical school.
 * Wheeljack's inventions blow up his lab every other day and it's rare whenever he makes something that doesn't blow up, unless the plot demands it. He also blows himself up constantly, causing Ratchet to have to curse and fix him constantly.
 * Red Alert's paranoia was increased by a 100 fold as fans took how he was in "Auto Berserk" and made that his default personality with him being paranoid about everything and occasionally glitching at them. That leads Inferno taking care of him.
 * Prowl's battle computer, will glitch out at illogical situations and he'll pass out. Also, he's a logical, emotionless, workaholic.
 * It can vary, but Bluestreak/Bumblebee tend to be found and raised by the 'bots an awful lot, and occasionally the twins, Prowl, and Jazz as well. This also leads to Blue being Prowl's adoptive son.
 * And these are just a few Autobot examples.
 * This also applies to couples, which is also in Ho Yay. Most of these are a given and when it reaches out it can seem weird.
 * Jazz/Prowl tend to usually be together in fanon.
 * Hound/Mirage as well.
 * Ratchet/Wheeljack is fairly common, or them just being best friends and Ratchet being with the twins. Yes, both of them. He also goes with Ironhide as well occasionally.
 * Bluestreak tends to also end up with Wheeljack or the twins, once again, a lot. This tends to coincide with Ratchet, as it happens when either one has Wheeljack.
 * Red Alert/Inferno, for obviously reasons. Though it's debatable if it's canon or not.
 * Ironhide tends to be with either Ratchet or Optimus, people don't really remember Chromia that much, but still he ends up with her when she's actually around.
 * Knock Out is almost always portrayed as gay and is usually paired with his partner Breakdown.
 * And so on, with more couples than there are letters on a keyboard.

Other Cartoons

 * Gadget and the Gadgetinis, a sequel of Inspector Gadget, inspired a fan to post information about a false third series called "Go Go Gadegetinis" on imdb.com and Wikipedia. In this "show" Gadget is paired with a female Inspector Prince. In addition to providing an explanation for Penny's parents, they got in the crossfire between Gagdet and MAD and died, Dr. Claw is finally captured and Gadget and Prince are married at the end. The article on Wikipedia still references this hoax.
 * Kim Possible
 * Fanwriters had long assumed that Kim's mother had the given name Anne, as her two brothers are named for her father's first and middle names, since "Anne" is Kim's middle name. In the last episode, Kim's mother is addressed as Annie by Uncle Slim, meaning in all likelihood this was right all along. The creators participated in a few online forums from time to time, and it's possible they made the decision to give her this name only after so many people asked about it.
 * The popular notion of feelings between Kim and Shego, be it one-sided or not. Then there's also the notion that Shego would become a teacher if she gave up her life of crime.
 * Another fan theory that has been prevalent in the fan-fics is that Ron is still receiving a percentage from Bueno Nacho, and that his parents had the foresight to set up a trust fund for him.
 * Code Lyoko
 * A lot of fanfiction has the story set in Boulogne-Billancourt, an area near Paris, France, because that's where the factory that the show's Factory was based off of once was. The name of the show's city has never actually been said - and don't even try looking to the dub for answers.
 * In the upcoming series of Code Lyoko prose novels, the city is named "The City of The Iron Tower, France". Which can be assumed to be Paris...despite the strange terminology.
 * Another thing that's never really stated is that (most of) The Men in Black, who appear throughout the show, are from this same organization. It's probably pretty easy to assume, though. Franz Hopper working against PC... men in black suits show up to take him away...
 * Since the characters have really slanted eyes with little black dots as pupils, people keep creating fanon eye colors for them. Some characters have had eye colors animated—Aelita has been shown to have Green Eyes on multiple occasions, Ulrich sometimes has brown eyes in earlier episodes, and William('s clone) was shown to have dark blue eyes in one Season 4 episode. As for the rest, fans generally agree that Jérémie's eyes are light blue, Yumi's are some dark/black color, and Odd's are purple, green, or in some cases both.
 * Because Jérémie tends to spend more time working on programs for Lyoko than actually spending time with Aelita, fans assume she and his computer have an intense rivalry. She rarely calls him out on this in the series, and actually seems to accept it later.
 * The computer game that Mr. Delmas is sometimes seen playing is never named in the show, but has been dubbed "Penguin Recaptiatior 3000" by fans.
 * It's been stated in-universe that, after one is devirtualised, an extended period of time must pass before that person can be revirtualised. It's never explained why, but many fans suggest that going to and from Lyoko is an exhausting process, and being virtualised more than once in a short space of time could be dangerous. Another suggestion is that the Supercomputer has to recompile the Avatars after devirtualisation.
 * Winx Club: Tecna is nigh-universally referred to as half-android, even though the only legitimate hint to such is a few throwaway lines in the non-4Kids dub of one scene in an S1 episode: "I've not been programmed for dating." "I'm going to go switch myself off now." (Goes off to sleep) Check it.
 * X-Men: Evolution:
 * A few fanfic writers made Rogue a fan of Anne Rice after seeing that she had a taste for vampire novels in the episode "Spykecam".
 * The other cases: Kitty being a fan of both Twilight and Taylor Swift is now a common belief due to her teenybopper personality. Jean is often assumed to wear thongs, while everyone at one point is refferenced as wearing a thong in fanfics she's the only one consistantly described as wearing them, (Funnily enough, the only character 'confirmed' as wearing thongs is Rogue, as goes a piece of Artwork made by Evolution's head artist Steven E Gordon), and that her hair is dyed red, born from Tabitha's comment in one episode and the Fan Dumb wanting to insult her. Kurt is assumed to cut himself in the darker more angsty fics who see him as a Sad Clown. Bobby is almost always depicted as a prankster, despite not actually pulling any pranks in the show, crazy shinanigans, but no pranks. Jubilee is often made into a tomboy, despite not even dressing like one (Wearing a feminine coat and boots) because of her status as One of the Boys (And possibly her appearence in the Tie In comics in which she appears to be quite sporty). Tabitha being the girl who Really Gets Around because she flirts a lot (A part of the double standard the Fan Dumb has towards the girls of the show), but it may just be a case of them being in high school.
 * Futurama: In fanfics, Fry's middle name is almost always James or John. Officially, it's "Jay", same as Homer Simpson.
 * Danny Phantom has some.
 * Most fans believe Paulina's last name is Sanchez, that Lancer's first name is William (after William Shakespeare), that Ghost Writer's name is really Devan (meaning poet), that Danny's middle name is James, and fans are divided as to whether Vlad has a ghost sense or not. Most people also believe that Ember's inspiration for RemEmber was a disloyal boyfriend.
 * The theory that one of Danny's ghost powers include faster healing. It does explain the Amusing Injuries.
 * South Park
 * About every third fanfic mentions Kyle's gorgeous green eyes. But on the show, his eyes are drawn as white ovals with black dots for pupils. Who knows what Matt and Trey would say if you asked them what color Kyle's eyes really are.
 * Kyle is, in fact, the only one of his friends whose eye color has not been mentioned. Stan has blue, Kenny's blue (originally both brown and hazel), and Cartman has brown (originally hazel).
 * Another part of fanon is that most of the cast is gay (not bi, though). Most of the boys, even Eric, have shown interest in girls on more then one occasion. Fanon never doubts that Butter is a flaming Camp Gay with a crush on either Cartman or Kenny. Besides Kenny and Stan, he may be the boy to have his sexuality stated most often. He's a Camp Straight.
 * Invader Zim
 * Anything about Irken mating is fanon. This includes various ideas, like that they lay eggs, males can become pregnant or, for that matter, that they mate at all, since from what one sees on the show it all seems to be done in a factory.
 * Dib and Gaz's last name is Membrane, since their father is "Professor Membrane." Word of God says that Membrane is the Professor's first name; the creators didn't want to give Dib a last name.
 * Questions of Dib and Gaz's mom. There are two general theories on this: one is that they had a mom (usually a Mary Sue who looked a lot like Gaz) and that she died, often in some sort of lab accident. This can lead to angst for all the surviving family members, including Membrane (his workaholism is often linked to grief). The other theory is that Membrane created Dib as a lab experiment, a storyline Eric Trueheart claims they might have pursued if the show hadn't been cancelled. How Gaz fits into that theory is up to the fan to decide.
 * Many ZATR fans seem to assume that Zim and Tak knew each other before meeting on Earth; often this is taken so far as to make them best friends. Zim makes no sign of recognizing her when they meet on the show.
 * Word of God on the subject of Zim's age is that he is "older than any human alive." Somehow this extremely open-ended time range has mutated into "150" (which is rather near the lower bound), but "16 in Irken years", significantly narrowing the gap between Zim and his main "rival", relatively speaking. Needless to say, the term "Irken years" never appears anywhere near anything coming from the official show or staff, but that hasn't stopped zealous fans from listing it as fact on Wikipedia.
 * Adventures of the Galaxy Rangers, because of the relatively small size and inter-connectivity of its fanfic writing base, has a lot of solid fanon elements.
 * Giving Niko a surname, Dal'Ariel (Niko Dal'Ariel meaning "Niko, student of Ariel"). When Koch Vision sent out a press release regarding putting the series on DVD, they included the fanon surname. The fanbase then had to admit to Koch that it was "just" fanon.
 * Among GR's fanon: Doc wasn't always on the "right" side of the law, is a lapsed Catholic, and is the black sheep of a very wealthy family. Zach's father was a nasty drunk, and that he's closer to Eliza's family than he ever was his own. Niko's Doomed Hometown was destroyed because of anti-telepath prejudice. Also, fanon states that the Rangers are loved on frontier worlds, but barely tolerated on Earth.
 * The Real Ghostbusters has a bit of this. For example, it's generally accepted that Winston was in Nam and Egon makes great cocoa.
 * Total Drama Island
 * Ezekiel gets a ton of this, since his personality was largely undeveloped before season three (which didn't really help things, since he was immediately voted off and driven insane...) Common elements include him being a great cook (canonically his parents are both Home Ec teachers) and that he hates taking off his hat (based on the fact that he never took it off on the show, before the aforementioned insanity).
 * Noah is gay, specifically for Cody, who in fanon is usually bisexual. Also, Eva is often assumed to be a lesbian, though this is less common and less rigorously defended, for some reason. Hey, it's not like the creators are doing anything to discourage this. Even fans who don't ship NoCo usually assume that Noah and Cody are close friends, mostly likely because they're both Ensemble Darkhorses and have enough similarities and differences to make good Foils. On the show they've only interacted a few times, often teasing each other (though not necessarily in an unfriendly way).
 * It's commonly assumed that Courtney's parents push her very hard to succeed, as a way of explaining her very driven and occasionally unpleasant personality.
 * At one point during the "Team Gwen vs. Team Trent" war, someone on a forum suddenly declared themselves on "Team The Intern" (referring to the blond one) and it was soon noted that he looked sort of like Billy Idol. The whole fandom now knows him as Billy the Intern, to the point where it's been used on the show's official blog.
 * If it's a SpongeBob SquarePants fanfic starring Squilliam Fancyson, expect him to be either quite sexually promiscuous or a god in bed. Possibly both. He's probably popular in Japan.
 * Phineas and Ferb
 * Any information about their missing biological parents is Fanon and unimportant as far as the creators are concerned. This includes the very interesting idea that.
 * Also their ages, though the non-canonical pilot episode says they're 9. The episode "Quantum Boogaloo" seems to imply they're 10, but Word of God says this may not be exact. A common piece of fanon used to be that Ferb was older than Phineas, most likely because he's taller, has a deeper voice, is more subdued and actually expresses an interest in girls. Again, Word of God discounted that, saying the two are the same age.
 * Lots of fans believe that Ginger (the Asian Fireside Girl) is Stacy's little sister.
 * Contrary to popular belief, Baljeet's last name is Raj, not Patel (though it is his friend Mishti's surname last name).
 * It's also a popular theory, at least among Perry/Doofenshmirtz shippers, that Perry is afraid of thunderstorms.
 * General consensus for the fans is that Jimmy Two-Shoes takes place in Hell or some other form of the afterlife. This was the original idea for the show that was scrapped by executives for being too hard to sell to distributors, and is never stated in the show itself, but with all the imagery people still accept it.
 * Archie of Class of the Titans is generally regarded to be a poet, and knowledgeable about such. This seemingly stems from the fact that he mentions having read some Greek poetry in his first appearance.
 * Teen Titans
 * A lot of fanfiction has Starfire referring to all her friends as "Friend *insert name here*" despite there never being evidence of her doing this in the show.
 * The fandom agrees that Jump City - where the show is set - is in California.
 * This was semi-confirmed in a promo video which advertised the third season and made the rounds at conventions in 2004. It previewed the "Titans East" storyline by showing a map of the US with the location of each team highlighted. The main team was clearly located in California, while the East team appeared to be in New York. The map never showed up on the show itself, though.
 * Robin is apparently an insomniac. Considering how obsessive he can get when hunting criminals, it's not too much of a stretch.
 * Some fan art for The Amazing World of Gumball depicts Penny as a doe with a removable peanut shell (It Makes Sense in Context).
 * The fandom of Daria, being fairly small and close-knit, tends to have some fairly standard fanon interpretations.
 * DeMartino is almost always a military veteran, having usually served in The Vietnam War.
 * Several of the Background characters have been given fanon names and personalities, some of which were based on actual production notes or semi-canonical materials (for example, when we see Mr. O'Neill's seating chart in one episode).
 * It is often assumed that Tiffany is adopted, since she is Asian but has the surname "Blum-Deckler."
 * In Goof Troop canon, 'Black' Pete is an extremely strict father to his son PJ, with a relationship based on fear and control, and PJ can't wait to move out of his dad's house. This is especially obvious when compared with Goofy's lighter, more open approach to fatherhood. In fanon this has been Flanderised and it is generally accepted that Pete is an abusive father - however the degree of abuse is debated. In canon there has been no evidence that Pete is physically abusive.
 * In Young Justice fanfics, it seems to be quite common to assume that Wally's parents are abusive. While this is true in other continuities, their few appearances (in the show and tie-in comic) and Word of God discount this theory. (Indeed, they seem to be the only parents on the show who don't give their kid some kind of baggage.)
 * In the Making Fiends fandom it's most common to make Vendetta a Eerie Pale-Skinned Brunette and Charlotte a Dumb Blonde. In canon they're both green and blue respectively. Fanon also typically make Charlotte an orphan; in canon Charlotte's parents are said to "be in space" however it is implied, though never confirmed, that they died.
 * A good majority of the Ed, Edd 'n' Eddy fandom has accepted Edd as being a blonde and Eddy as being a raven; in the cartoon only Ed has an confirmed hair color (red).
 * For fan-artists who draw the Edd's in the shows style, it's very common for an older Edd to be drawn with long black hair.
 * In Adventure Time, the Rule 63 world is sometimes referred to as "the Land of Aaa," even though the "Fionna and Cake" episode still uses "Ooo."