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 Fan Fic.
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 puts himself in danger to retrieve Rumble, Frenzy and Laserbeak when they sustain heavy damage. He also displays this trait in the Transformers Prime episode, Triage, where he goes to save Laserbeak instead of finishing off Wheeljack.
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.
More specifically, Starscream, Skywarp and Thundercracker are usually portrayed as brothers, either as triplets, or with either Starscream or Thundercracker as the eldest and Skywarp or Starscream as the youngest.
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.
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 extremelyprotective of them, which is said to be true for all Seekers (who are portrayed as a sort of sub-species of Cybertronians).
Starscream is a member of the Royal Family of Vos - either A prince, or THE prince.
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.
Usually doesn't begin to cover it. Even in fic that's nearly completely het, Jazz/Prowl are still likely to be a side pairing.
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.
Megatron/Starscream is extremely popular. Must be all the Foe Yay.
And so on, with more couples than there are letters on a keyboard.
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.
Also, after The Last Roundup, her personality has started to consistently be Derpy just being a clumsy but hardworking mare.
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.
Though this one's still up in the air, considering her brother's name is "Shining Armor".
Some people simply don't care and say Twilight's brother's full name is actually "Shining Armor Sparkle".
This was Jossed by Pinkie Pie and the Rockin' Ponypalooa Party!. Her parents' names are Igneous Rock and Cloudy Quartz (father and mother respectively), and her sisters are Marble Pie (the blue one) and Limestone Pie (the grey one).
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 a G1 pony with the same mark and similar colors.
Bonbon will occasionally be a Jerk Ass 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 the Season 2 finale 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 herobsessionwithattaininghands, 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.
Vinyl Scratch and Octavia are starting to become the fandom's secondOne True Pairing, due to very well-written fanfics such as "Allegrezza" and "The Vinyl Scratch Tapes".
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 sixnote Many artists also choose to because the darker skin tone looks best with the palette of purples; one of the most popular pony fanartists, Yamino, also claims Twilight reminds her of a Sri Lankan she once knew), and seems to really, really like lavender sweater vests. No one knows why, though the second can be attributed to sweater vests being associated with intelligent and/or academic characters. Similarly, Applejack wears cowboy-ish clothing (typically with short shorts, no matter how impractical that really is), Rarity dresses stylishly and lady-like (typically she wears fashion from The Roaring Twenties), and Rainbow Dash dresses tomboyishly, often in sweatshirts or track jackets.
Human!Twilight's typically drawn in a school uniform, and even in casual wear she's prone to sweater vests. Human!Rainbow Dash is almost always drawn flat-chested, Human!Celestia often has rather dark skin (being a sun goddess and all), with Luna being very pale. 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. She's also rather likely to be portrayed as chubby due to her love of eatingsweets.
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 and human!Twilight (given the latter's Hime Cut hairstyle and both characters' Tsurime Eyes).
Human!Fluttershy is almost always depicted as a Sweater Girl, with the sweaters almost always being yellow to match her fur color as a mare.
Fluttershy as a MtF Transsexual is another popular one.
Another common depiction for Fluttershy is to give her large breasts. The main reason for this is because nurturers tend to be drawn in art as overly busty. This has lead to the popular Fan Nickname of "Hootershy".
Pretty much all of the Mane Cast have nicknames for their large-breasted personas: Rainboob Dash, Headlight Sparkle, Applerack, Raritits, Pinkie Pies, and the above stated Hootershy.
Flying for Pegasi is often changed into running, though occasionally you'll see it made into flying with jet planes. Or motorcycles.
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. This came from a piece of fanart that had Luna (who was imprisoned in the moon for the last thousand years) shocked to see stallions 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".
Alternatively, he is also known to be called "Orion" from time to time.
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!
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).
It's not exactly rare to see Cheerilee as Scootaloo's sister, half-sister, or sister figure due to the fact they were siblings in G3.
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 only been called it once or twice in season 2)
The Mane Cast often goes by specific names when their gendersare swapped. Rainbow Dash becomes Rainbow Blitz, Twilight Sparkle becomes Dusk Shine, Rarity becomes Elusive, Fluttershy becomes Butterscotch, Pinkie Pie becomes Bubble Berry (or occasionally Berry Bubble), and Spike becomes Barbara. Applejack's name is usually considered gender-neutral and left alone.
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 GirlPyro Maniac. 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), or a companion to Pinkie due to their love of cupcakes.
Similarly, toyline-only pony Star Swirl is often thought to be the descendant of Star Swirl the Bearded, due to them sharing a name. Though the fandom generally Retcons her into a Unicorn rather than go with her canon Earth Pony depiction.
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".
However, most just call Lauren Faust's alicorn "Fausticorn" or simply "Lauren Faust". Occasionally known as "Queen Faust".
Bonnie Zacherle, creator of the original My Little Pony, is also usually depicted as an alicorn - often as Fausticorn's teacher.
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.
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. The part that griffons have a country is possibly confirmed (depending on its canonicity) in the Pinkie Pie micro comic, when she mentions the Griffon Kingdom.
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 twisted versions of the G1 Flutter Ponies.
Popular Fanon in general about the Changelings is them operating as a eusocial insect or Hive society with Chrysalis being the mother of the race. This is despite the fact that during their limited screen time in the show and the comics there has been absolutely no solid evidence or reference whatsoever of a "hive" or Chrysalis herself referring to Changelings (the most of whom we have seen as soldiers in Chrysalis' army) as her "children" or "drones".
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.
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, here and this fanfiction.
One bit of persistent fanon is Octavia's mother being a Beloved Smother. This goes from the usual Education Mama-type, in which she demands Octavia practice her cello so she can join a prestigious orchestra, all the way up to an Evil Matriarch who actively attempts to sabotage her relationship with Vinyl Scratch (due to a related bit of fanon that Octavia's mother is very homophobic).
Discord is often shown to be Luna and Celestia's childhood friend, until something went wrong. Either as a follow-up or alternative, he is also shown to have been in love with Celestia.
In "Luna Eclisped" the carriage of the Princess was pulled by two pegasi guards with bat wings and darker furs and armors than usually. Since the episode took place on Nightmare Night, the pony version of Halloween, it was probably just a costume. Many fans, however, liked the idea of Luna having her own guard of bat-winged pegasi and there’s quite a bit of Fan art of the “Night Guard”.
As of late, the idea of Luna having a "Night Court"note Probably not that Night Court (afflicted with varying degrees of corruption) has also become rather popular.
The "Bat-ponies" have since taken off in the fandom (or Thestrals, as they are sometimes called). Two characters in particular, both female, seem to pop up regularly in fan-art and fanfiction, named Angel (from The Golden Armor) and Midnight Blossom (from the NSFW Clopfic A Tryst at Midnight)
Fans seem to have grown attached to the idea that as a kid, Twilight Sparkle liked to build book forts.
Since some episodes have confirmed that Equestria uses the same days of the week as Earth, people have assumed the ponies use the same months as well, but not the same years. Many fanfic writers make Nightmare Moon's banishment as Year Zero. Modern day Equestria, then, as of this writing, is in the year 1002 CE (Celestial Era, a play-on-words with Common Era).
Sometimes, they use "ANM" (After Nightmare Moon), or alternatively, "RPL" (Return of Princess Luna). But the latter much more so.
On the subject of time, many fans believe that one year passes for each season of the show. There's really nothing to support this, and the opening of season 4 suggests that everything up to that point happened over the course of one year.
Some fans assume that each of the pony races age at different rates and have different lifespans, with unicorns living much longer then earth ponies (similar to Elves and Humans). Pegasi lifespan vary, but usually they live as long as unicorns.
Other fans assume the opposite, saying that earth ponies have longer lifespans than unicorns due to the earth ponies having a stronger connection to the planet, and unicorns "burning brightly, but for a (relatively) short time". Pegasi are still considered middle-of-the-road.
Yet another faction has pegasi dead-last in the lifespans department. While Unicorns may be "magical elves" and Earth Ponies are "connected to the earth," Pegasi life fast and die young. This comes from them being more prone to injury(flying ponies and cloud cities mean long falls) and wing failure as they get older.
Another persuasive idea is that Earth ponies are often looked down upon by both the Pegasi and Unicorns for being "inferior" due to a lack of wings or magic. Fans also assume that there is a sort of Fantastic Caste System in place with the Unicorns on the top and the Earth Ponies at the bottom. Nevermind the fact that this sort of thinking almost drove them all to near-extinction according to the Hearth's Warming Eve pageant.
Due to the number of stallions versus mares shown on-screen at any time, many fans assume there to be an actual diparity in gender populations. Whether this is genetic or merely some sort of segregation depends on the author.
Also serves as an unintentional Furry Reminder, as real-life horse herds will only have a few stallions at most. And, seeing as two mares rule, they also assume that like real horse herds, ponies are matriarchal.
Also possibly explained in some fics that Ponyville is a mostly lesbian town. Other settlements are more balanced and heterosexual in nature.
Earlier in the fandom there's was fanon for G1 and G2 that when foals grew up their colors, and Cutie Marks changed, and they choose a new name. It was especially common for G1 where the baby ponies mostly looked like their parents.
As unicorns and pegasi have canon abilities unique to their races (magic, and flying/weather control, respectively), it's very common for fans to portray the earth ponies as having Super Strength and/or Green Thumb abilities so that their general power level is even with the other races. The former, while not outright stated, is implied, as Big Macintosh has no trouble dragging a house, and Pinkie's sister Maud is capable of drilling through solid stone with her bare hooves and throwing a large rock an incredible distance without even trying.
People often make King Sombra Large and in Charge, going with the whole "royalty = bigger" thing the show has going (in-show it's unknown how tall he is)
Everyone writes Applejack and Scootaloo as being an orphan/having dead parents.
After her appearance in Hurricane Fluttershy, background pony Blossomforth is often portrayed as a contortionist based on her contorted pose in that episode.
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.
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.
Shego's name was never shown but it's common for fans to call her "Sheila".
A relatively less likely to be contested one is that Jet's Freedom Fighters all go by nicknames assigned by their leader Jet.
The idea that Kyoshi solved all her problems with violence and bathed in the blood of her enemies tends to be really common as well, all because she readily accepted responsibility for the death of Chin the Conqueror (and made it clear that she would have been willing to kill him, had he not fallen off a cliff) and counselled Aang to kill Ozai.
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.
There is a certain level of truth to this, in that at least this is what is believed to happen in-universe. According to Avatar: The Last Airbender - The Search, the Fire Sages felt that the offspring of the Fire Nation Royal Family and Avatar Roku's descendants would produce powerful firebenders. The results were Zuko and Azula, the latter considered a success, the former a failure.
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 100% lesbian. 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 a flaming dyke.(Pun intended.) She's also a serial rapist, if you believe the fanon. Her victims include Mai, Ty Lee, Suki, Sokka and Zuko.
Any contention over Azula's sexual orientation will likely not be over whether she is into women, but whether she's also into men. This troper has never seen anyone try to argue that Azula is completely heterosexual.
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 of the 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...
It's pretty well accepted in the fandom that Azula and Ty Lee are actually together and the writers managed to sneak it under the radar, to the point where they are often listed as a canon pairing. This despite the fact that there is actually a scene in season 3 where Ty Lee gives Azula advice about flirting with boys, which Azula promptly puts into motion. That being said, there is a lot of subtext between the two (but then, Azula has subtext with everyone including her brother, and Ty Lee will flirt with just about anyone), it is pretty clear that Azula cares about Ty Lee more than she cares about anyone else, except for maybe Ozai, and Ty Lee seems absolutely devoted to Azula, up until The Boiling Rock. The fact that Azula's feelings toward Ty Lee later got a Word of St. Paul confirmation may have helped this particular theory along.
Going hand-in-hand with the above point, the idea that Ty Lee is bisexual has become quite well-accepted. She is not generally interpreted as a lesbian, probably because she is shown to clearly be interested in men on a relatively regular basis and even comes on to Sokka pretty heavily, but her behavior toward Azula is eyebrow-raising enough that it seems no one really thinks she's straight either, despite the gender of the person she is actually being shipped with. It doesn't hurt that she flirts withanyone and everyone.
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 Bishōnen 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, when in canon, she calls people by name in serious moments. 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'.
In most fanfics featuring Zuko's daughter, she is named either Ursa or Honora.
It's commonly agreed on by most fanfic writers that Ozai abused Azula as well as Zuko, physically, emotionally, sexually, or a combination of all three.
The physical abuse toward Zuko, as well as psychological abuse toward both Zuko and Azula, is actually canon. That being said, it is very difficult to find a fanfiction that goes into even a moderate amount of detail about Azula and Ozai's relationship and doesn't include sexual abuse.
Most fanfic authors also agree that Suki was tortured during her time at the Boiling Rock. This idea isn't unfounded. She was the leader of the group of warriors found in the company of the avatar's flying bison, so it makes sense that she might have some information on his whereabouts, and the guards at the Boiling Rock do torture prisonersfor information in canon. However, some fans crank it Up to Eleven, taking Azula's infamous "favorite prisoner" comment to mean that Azula either raped Suki or had the guards rape her. Azula clearly intends to imply something along those lines, but many fans believe that she only made that remark to get a rise out of Sokka and none of it was true. Suki's behavior after her rescue doesn't seem to reflect that occurrence either.
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).
The idea that Kya is a lesbian is gaining a lot of traction. Some fans use this to ship with her with Lin. Others just like the idea.
The identity of the mother of Zuko's daughter hasn't been revealed, but fans almost always assume that it's Mai. This is probably in part because she was Zuko's only canon love interest in the original series who lasted longer than one episode, and in part because her only major rival shipping-wise is canonically paired with Aang. It does seem probable. Even though Mai broke up with Zuko in the comics, they are both shown to still love each other.
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.
In the 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 Project Carthage. 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. (CLE character models confirmed his eyes to be brown.)
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.
Word of God answered this question in a french interview: the Lyoko-Warriors can't revirtualize because they are too exhausted by the experience and need to rest before going again. Code Lyoko: Evolution quantified the cooldown period as twelve hours.
Even though the heroes were initially never named in-universe, the fans have came up with two names for the team: Team Lyoko and Lyoko-Warriors. While the first was never used in the whole series, Lyoko-Warriors became Ascended Fanon starting with season 3.
Similarly, fans referred to William as a "Xana-Warrior" after he was turned into XANA's Dragon, though the term was never actually used in-story.
Although it is never directly stated, it is interpreted that hair of any color (such as Aelita and Anthea's pink and William's mother's green) is genetically possible in the Code Lyoko world, although colors other than black/brown/blonde/red are highly uncommon.
Franz Hopper's one dramatic gesture with his coffee cup has led fans to believe that he has a great love of coffee.
It's surprisingly common (or maybe not so surprising) for fanfic authors to make Ulrich's dad psychologically abusive despite there being no real evidence in-universe (and at least a couple of pieces of evidence against it: Ulrich only seems worried about disappointing his dad and is eventually shown to be completely unafraid of telling him where to stick it).
Winx Club: Tecna is often 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).
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".
Some fanworks portray Kitty being a fan of both Twilight and Taylor Swift, 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.
While it's a common fan-depiction for the character across other X-Men incarnations due to the idea of her absorption powers affecting her mental state, the Evolution incarnation of Rogue is the only one where the fandom idea of her being bisexual is usually portrayed as being a natural part of her personality rather than influence from her powers, though it's possible this might mostly stem from the Evo version's Goth/punk aesthetic and the stereotype of Goth girls as usually being bi.
Futurama: In fanfics, Fry's middle name is almost always James or John. Officially, it's "Jay", same as Homer Simpson.
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.
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, and Kenny's are blue (originally hazel in a draft for "Bigger, Longer, and Uncut" note though a gouged-out eye of his was shown to be blue in "Starvin' Marvin". Some also believe he had brown eyes, due to an ass pun Cartman made about Kenny having a "brown eye" when he put a picture of Kenny's butt as a missing child poster). Cartman is usually speculated to have brown eyes, although some will also give him blue or hazel due to the fact that he harvested Kenny's eyes for his own sight at the end of "The Succubus" (although being that the show can rely on Negative Continuity, this detail may also be suspect).
Strangely, Japanese fanartists tend to give Kyle brown or reddish eyes rather then the green western fans go for.
Before Kyle's hair was revealed to be red (and in his "Jewfro"), a lot of fanarts went with giving him straight brown hair or even black hair like Stan's. Those that did give him curly hair like Matt Stone still didn't take it as far as the show did!
Most characters have a set fanon eye color. You'll rarely see Butters or Craig with any color other than blue, brown is the most common eye color for Tweek, both blue and brown eyes are extremely common for Clyde, etc..
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 Butters 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.
Although Clyde's status as the "second fattest" kid was just a guess by Butters that Stan and Kyle jumped at for the chance of having a replacement to mock in Cartman's absence, there are fans that insist on drawing him just the least bit thicker than the other skinnier kids, or making him outright chubby, though with some muscle to contrast Cartman.
There are a lot of fanon names and relationships that have perpetuated and been mistaken for actual canon due to some fans' persistence. These include: Kevin Stoley note The Star Wars-obsessed kid who may or may not be Asian, depending on the episode/season and Esther note One of the background girls who got to speak once in season 6 being fraternal twins due to both having black hair and similar clothing color schemes, Craig's sister being named "Ruby", Kenny's mother being named "Carol" note Which was a name once used for Stan and Kyle's moms in "Death" before they got their official names. Word of God as far back as 1999 was that she had no name., Kenny's sister being named "Karen" (which did eventually become Ascended Fanon), Craig's father and Skeeter (the town redneck) being brothers, Red being Craig's cousin (due to Skeeter once implying she was his daughter), and other assorted details that usually apply to secondary/background classmates or the boys' siblings.
Back in the pre-season 5 days of fandom, some fanfiction and sites assumed that Butters' real name was "Jim Swanson", due to him being referred to as "Swanson" in the "Conjoined Fetus Lady" script and episode, and a fan mishearing "Jill" (the character Butters was playing in the "Charlie's Angels" game in "Two Guys Naked In A Hot Tub") as "Jim". The Swanson name was put to rest when his surname of "Stotch" was revealed, though a later character named Jimmy did have the Swanson surname before the creators changed it to Valmer.
Another longstanding fanon was Kevin Stoley's surname beginning with a "C", based on mishearing his first canon name "Casey" as "K.C.". This lead to him being referred to as "Kevin C." in many fansites, though fans would rarely expand on what the C would stand for (although it would sometimes be "Charles" or "Chang", the latter to reinforce his Chinese heritage). "Kevin Mattrei" was also once used in fanfiction, but did not catch on for very long. Those who want to preserve the "C" have moved it to being Kevin's middle name, while keeping the Stoley surname.
Other fanfiction names that briefly were used and passed around included Kenny's mother being named "Peggy" (before "Carol" came into popularity), Craig having "Nommel" as a surname, and the male Goth Kids being named Ethan (The tall goth), Dylan (Red-haired goth), and Georgie (The "Kindergoth"). The one-shot movie characters Christophe (aka "The Mole") and Gregory received the respective fanon surnames of DeLorne and Thorne from a fanfic, which wound up spread around for a few years.
The goth kids did eventually wind up receiving canon names in season 17: The red-haired goth was christened "Pete", the tall one as "Michael", and the kindergartener as "Firkle".
Though an age difference (if any) was never given between the one-shot Cotswolds siblings in season 3, some fans have Rebecca as a year younger than Mark (making her technically a 2nd-grader when she appeared), or some will depict them as fraternal twins and Mark as the elder one. Kenny's brief girlfriend Kelly also has some fanon circulating about her, such as the surname "Nelson" note based off of a throwaway line in a later season where Cartman mentions tricking a girl named Kelly Nelson into smelling his finger, while Kenny was shown to look annoyed (leading some to assume the Kelly was his girlfriend), or that Sally Darson from "Butters' Bottom Bitch" is her cousin or twin sister, due to their similar appearances.
Red note although also given the one-time names of "Bertha" and "Rebecca" had quite a few fanon names and characterizations before the show writers decided to utilize her more with the other girls. In particular an early Pip-centric writer or two had latched on to her being seen with Pip in "Mr. Hankey the Christmas Poo" and "Summer Sucks" and called her "Biddy", after a character in Great Expectations (who had feelings for Pip). Others called her "Rachel" or "Mollie". Because she was either completely silent pre-season 6 or still didn't speak as much for a while after, she was a blank slate and portrayed as a silent stoic, an easily-frustrated foil to Wendy and Bebe, or more tomboyish. Some also latched on to the idea of portraying her as someone who has quite the lovers in aged-up fanworks, going off how the animators used to pair her off with Kevin for scenes, her angry jealous moment at seeing Rebecca Cotswolds flirt with Token in "Hooked On Monkey Fonics", and her being paired off with Annie in later background scenes.
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. A particularly common iteration is that Dib is a clone of Membrane, and often that Gaz is a clone of Membrane's deceased wife.
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.
Fans just about unanimously refer to the species from Vort as "Vortians," though the show actually refers to them as "Vorts." It is also quite common to claim that they are a species of scientists, which is never stated but rather plausible (Prisoner 777 and Lard Nar were both inventors and much of the Irkens' technology seems designed by willing or enslaved Vorts).
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.
Ezekiel gets a ton of this, since his personality was largely undeveloped before season three. 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, at least until he turns into a gollum in season three).
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.
Not necessarily. They could have meant they were the same age in the legal sense. If you and your friend are only born, say, 2 weeks apart, the two of you will still legally be the same age, but whichever of you was born first is still older.
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.
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.
Quite a bit about Raven actually: that she has a Hair-Trigger Temper, that she often responds to aggravation with bodily harm (the "throwing Beast Boy out of a window" bit is especially ubiquitous), that she can't smile for fear of her powers (even though she does so, while not all the time, fairly often in the show), that she can't show any emotion except for the aforementioned temper without her powers exploding (especially not true, as what makes her powers go out of control in the show is either an excessive amount or denial of her emotions, not showing them in general and, again, she shows a good range of emotion on the show) and a whole plethora of cliche Goth tropes are all taken as fact by the fanbase or fanfic writers despite no real proof from the show itself.
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."
Jake's side of the family, as well as Tiffany, are often presumed to be Jewish due to their surnames. Word of God says he intended "Morgendorffer" to sound German rather than Jewish. For what it's worth we see once that they own Christmas decorations.
In Goof Troop canon, 'Black' Pete is an extremely strict, psychologically abusive 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. Despite this, there has been no evidence that Pete is physically abusive. In fanon, on the other hand, it's generally accepted that he is to some degree, though some think he sparingly uses this method while others think he does it frequently.
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 Goddiscount this theory. Which is probably for purposes of contrast: Wally's co-stars have dead parents (Robin), supervillain parents (Aqualad, Artemis, Superboy), parents living on another planet (Miss Martian), and overprotective parents who have been possessed by the Helmet of Fate (Zatanna). Wally is the only member of the team to have a demonstrably stable, mundane home life with a boring nuclear family.
M.A.S.K fandom tens to put Brad Turner and Vanessa Warfield together thanks to thier clear chemistry in the episode "Cliff-Hanger". One fan even theorized that Vanessa was secretly working with M.A.S.K for much of the racing series and was slowly turning against V.E.N.O.M.
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 common fanon theory is that "Vendetta" isn't her real name. Most will go with Violet, after her mother Violeta (but never Viktoria, which would work better since it's a common Bulgarian girl's name, and makes her named after her father Viktor.)
A good majority of the Ed, Edd n Eddy fandom has accepted Edd as being a blond 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 most common for an older Edd to be drawn with long black hair; if not black then brown, but never blond.
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."
Generally people assume that facts about the normal world carry over to its gender bent counterpart—for example, that the Ice Queen knew Marshal Lee during the Mushroom War. However, many fans depict the Ice Queen not as a female version of Simon Petrikov, but as his fiancée Betty, suggesting that in this world his "gag" was putting the crown on her instead of himself.
For a long time fans assumed that the Lich was the cause of the Mushroom War; however, the season five opener implies that he was actually created by the war.
Most fanartists who draw Finn in a realistic or Animesque style ignore that he has bad teeth, he's a bit pudgy, and his hat is made from a bear's head; instead drawing him as a Bishōnen with normal features, perfect teeth and a fluffy fabric hat (or none at all).
It's also interesting to note that fanart usually shows some of his hair sticking out from under his hat, which only occasionally happens on the show. (This was popular even back when his hair color was only known through Word of God.)
Doctor Princess is said to resemble Betty, leading to speculation that they might be the same person (this was Jossed by Word of God).
Ever since the first real Chip 'n Dale Rescue Rangers fanfic Rhyme And Reason was released in 1996, Chip's last name has been Maplewood, and Dale's last name has been Oakmont. In the show itself, none of the Rangers has a canonical last name, even Gadget's supposed family name Hackwrench can only be deduced from her father's name Geegaw Hackwrench, but the name "Gadget Hackwrench" is never said nor written in any episode.
This is more common with the main Disney Chip and Dale, than this incarnation of them, but the two are seen as siblings (usually twins). In canon their relationship is unknown other than they're close friends.
Many Animaniacs fans will swear up and down that Yakko is left-handed and lactose intolerant with plenty of evidence to support the contrary (he's at most ambidextrous, and there were plenty of times he ingested dairy with no ill effects). Less accepted is that Wakko is hypoglycemic. The evidence is that he said it, but if that were true that would mean that every other thing else they've said is true, including things like the Warners literally, actually being Dr. Seuss knockoffs when they're just actors. The "just actors" thing seems to slip everyone's minds, including people that should know better. It's fine in moderation, but infuriating when people won't accept the evidence that's right in front of their face. Even worse is the fact that all three of these pieces of fanon came from ONE OBSERVATION of each, two of them throwaway gags (the two endocrine disorders). You know, For Science!
Even with being gag-oriented and having Negative Continuity that usually means there's no solid canon to go by (or perhaps because of this), Superjail! has collected some fanon over the years:
The Warden doesn't seem to have any other name (that we know anyway), but there are fans that will insist on naming him "David", after his voice actor David Wain (who he was modeled after).
Most characters don't have their eye colors depicted (except for in some shots or close ups), but there are fanartists that like going with the idea of Warden having Purple Eyes to accentuate his unusual nature.
Jared's assumed to have been abused by his parents as a child or that he was adopted, to add to the idea that his entire life has been filled with incidents of horrible luck.
Lord Stingray appears to be a white human male beneath his suit in "Stingstress" (although he never takes off his mask), although a fanon concept known as "Lord Beast Ray" was previously popularized by a Stingray roleplayer and other fanartists. Instead of being a man, Stingray was depicted as a yellow-skinned mutant creature with a face exactly the same as his mask, and spikes protruding from his back. Even after the show's reveal, Beast Ray continues to pop up here and there in fanworks.
Other fanon about his unmasked appearance has him as either a wicked and attractive blond man with sharp teeth, or as an evil doppelganger of the Warden with RED glasses, spiked black hair, and the sharp teeth.
There's the assumption and theory by some fan authors that the Warden or Mistress (or both) may secretly have feelings for the other. And then there are those who theorize that the two are actually long-lost siblings who never got to know each other (and thus making that time they slept together to be even more dysfunctional).
Based off the mind screw ending to "Terrorarium", there were fans that assumed the Twins to be part of a completely identical species and that they might not be brothers, either that or that they were only two of MANY brothers. The fake flashback in "Hot Chick" (to illustrate their lie about their past) seemed to play with the idea, but it was ultimately Jossed in season 3, where the Twins were revealed to be the younger siblings to a group of Triplets, and the five apparently being the only children of their overlord father.
Though it was never specified who exactly birthed Jacknife's illegitimate son, the popular fanon is that it was Lady Jacknife from "Stingstress". This is also coupled with the idea that she could be related to him in some way.