Never Live It Down/Western Animation

"Aquaman: King of the ocean, Remember?""
 * Haru from Avatar: The Last Airbender showed up in the third season with a dumb looking an ultra-sexy mustache, and the fandom still hadn't stopped making up jokes concerning it. This is partially because a certain Internet parody series played him as a self-absorbed Camp Gay pretty boy several weeks before he reappeared.
 * Canon example: Katara made one speech about hope and courage and freedom. The Ember Island Players's stage rendition of her was constantly waxing melodramatic about hope and "tearbending".
 * Sokka and Momo accidentally getting strung out on peyote for a day and a night in the desert.
 * IT'S A GIANT MUSHROOM!! MAYBE IT'S FRIENDLY!!!
 * Optimus Prime, similar to Jean Grey, has only sacrificed his life and revived a total of two times in the G1 cartoon, and another two in the Marvel Comic rendition.
 * That's just G1. In addition to those four instances, Optimus also dies  As the first time he did it was so shocking, fans and writers alike quickly latched onto the idea, and it seems the writers have gotten carried away. Now, if the current series' Optimus doesn't do this at least once, fans are disappointed, and it even got its own little Lampshade Hanging in Beast Wars. Currently, the Transformers Robots in Disguise incarnation is the only version of Optimus to not have died at least once (Transformers Prime is still young, and he doesn't die in Shattered Glass because that's Megatron's job.) Transformers Animated gets it out of the way in the series premiere (and even then, he was only dead for a little over a minute).
 * Hell, when G1 cartoon Optimus' backstory is revealed, we find he became Optimus in a We Can Rebuild Him situation - he was a civilian who was killed by Megatron soon after Megs' villain career began.
 * Ultra Magnus is only remembered by fans for the infamous movie line, "I can't deal with that, now". Not only has it become an internet meme, but it also forever painted Magnus in fans' minds as an arrogant and lazy commander who would rather pass off responsibilities to his subordinates than actually get his own hands dirty. The fact that he's seen coordinating strategies more often than he is executing them doesn't help matters much, but he is more proactive than this misconception paints him as being. On top of that, the original line was said as he was in the middle of trying to pilot a ship that was crashing, so it was less "Who cares?" and more "Kinda busy here!"
 * Remember how G1 Red Alert was always panicky and ultra-paranoid? If so, that makes one of us: In the aptly-named episode "Auto Berserk," when a missile hits him in the face, resulting in brain damage that would have killed him eventually, he starts acting in this manner, to the point of helping Starscream get his hands on a superweapon just to keep the Autobots, whom he believes have turned against him, away. He's fixed later. Fans seem to forget both that he was this way for one episode only due to damage, and quite how dangerous the paranoid schizophrenic Red Alert really was. Even his toy bios go on about his paranoia, as if something we've never witnessed in any episode or comic but the brain-damage situation was in fact his defining trait.
 * There's also Mix-Mix-Mixmaster's Verbal Tic of re-re-repeating the beginning of a sentence... some-some-something he only actually did in one ep-ep-episode (City of Steel.) Thank-thank-thankfully. Shrapnel, however, really did repeat the last word of every sentence almost every time he appeared, appeared.
 * Beast Wars once had a damaged Waspinator think he was Shrapnel... only to start talking like Mixmaster did in City of Steel.
 * Sentinel Prime may be going this way due to Transformers Animated, due to his smug attitude, general disrespect for others, and sometimes morally reprehensible techniques, in later continuities, there are some aspects of it, one of the names Zeta Prime has, suggested by the writer of Exodus is Sentinel Zeta Prime, and demonstrates much of the same behavior. The Sentinel in Dark of the Moon seems to avert this.
 * Ron in Kim Possible received Twenty Four Hour Superpowers at a rate not seen since Jimmy Olsen. For some reason fans latched onto his one time use of "Monkey Power" which influenced the writers to both tease and please fans with its usage in later episodes. Perhaps Everything Is Better With Monkeys.
 * The "Monkey Power" was never a 24 hour power though, it was a permanent change. Even Monkey Fist got imbued with it and kept it. Ron just could never get it to work more than intermittently.
 * A real example, though, is cooking. One episode shows Ron as a surprisingly excellent chef, while Kim is a disaster. Though she improves by the end of the episode and it's never mentioned again, in Fanon Ron is a god in the kitchen, while Kim's cooking defies physics with its hideousness.
 * Though not as prominent as the other examples, a few KP fanfics milk drama out of the fact that Ron essentially killed Warhok & Warmonga, despite the fact that a). said aliens, had they lived, would've no doubt come back to exact horrible revenge and b) it wasn't like he did it in cold blood; he just happened to toss them into their spaceship, which exploded. But for many authors, this was a Moral Event Horizon.
 * Not to mentioned that they threaten to kill Kim and mount her like a trophy.
 * Tygra in Thunder Cats is known as a weak-willed junkie, despite being addicted twice, only one of which was actually presented as a drug.
 * Comic Hero Aquaman is commonly haunted by his portrayal in the Super Friends cartoons, as a guy whose only real powers are swimming and talking to fish. This has actually worked out for him a little, as later iterations of the character usually go to great (and awesome) lengths to subvert this image.

"Bebe: Wendy broke up.
 * Wendy broke up with Stan exactly once, in the seventh season of South Park. They got back together in the eleventh season finale and have been together ever since. Yet fanfic writers tend to portray Wendy as a manipulative shrew who breaks Stan's heart again and again. This is usually done to justify Stan leaving her for Kyle. But even some writers who like Wendy latch onto the idea that she and Stan break up and make up all the time.
 * It may have more to do with the fact how shallow their relationship is shown at times. Both have shown heavy attractions to other characters in an extremely unsubtle manner (Stan once constantly attempted to make passes to a substitute teacher and even gloated about supposedly making love to her to Wendy's face while Wendy became disinterested in Stan in favor of another popular jock less than one season after they got back together). Their less than affectionate relationship was even Lampshaded in Raisins.

Stan: Wait what did I do wrong? I haven't talked to her for weeks!"

"Farnsworth: You take ONE nap in a ditch and people start declaring you this and that!"
 * In Teenage Mutant Ninja Turtles fandom, April O'Neil's yellow jumpsuit, her fucking jumpsuit. Honestly, every conversation about the old show dissolves into one about her hotness and jumpsuit, this has even made it into other adaptations, as a reference or actually happening (Hell, in the Back to the Sewers season of the 03 show, she wears one!).
 * The Fairly Odd Parents: The episode "Home Wrecker" had Tootie admitting, through Suspiciously Specific Denial, that she tapped Timmy's phones. "Just the Two of Us!" had Trixie going insane and attempting to kill Timmy when the two were the last humans on Earth. The detractors of both have not forgotten these incidents. And let's not forget, although in this case it's an example of the producers never living it down, the horrendous Wonderful Life Subversion episode, "It's A Wishful Life". It is still heavily criticized as one of the lowest points in the series.
 * On Codename Kids Next Door, Lizzie used a "Boyfriend Helmet" on Numbuh 1, and ordered him to destroy his teammates. In several future apperances, she was developed more, given her relationship more depth...but people's minds were already set. She became the single biggest target of Die for Our Ship in the fandom. Admittingly, she remained clingy, but nowhere close to that level.
 * In-universe example from Total Drama Island: Noah kissing Cody on the ear while they are both alseep in "The Big Sleep" is still remembered by campers well into season two. (For both of them--apparently being kissed makes Cody at least bisexual too.)
 * It's also remembered by the creators as well, see the Ho Yay section for more.
 * Ezekiel made one sexist comment during his short time on Total Drama Island. Two seasons later, even though others have shown far more sexist tendencies, Zeke was pretty much labeled Straw Misogynist, and is still hounded for it.
 * Similar to the Pikachu/ketchup example, Starfire of Teen Titans was shown drinking mustard once. It's common for it to be referenced in fan works.
 * She is, however, shown at several points later with a bottle of mustard with a straw in it in the background, even if she's not actually in the process of drinking it.
 * Spider Man the Animated Series - whole show, for the censorship issue. Yes, they couldn't say "die" or "kill," have Morbius suck blood, or have Spidey full-on punch anyone. But it seems that's all anyone says about it lately. In fact, it was an ambitious arc-based series with a lot of depth, emotion, surprises, and the portrayal of Venom that has impacted every adaptation since. Interviews with showrunner John Semper reveal that as it was on FOX - yeah, that Fox - it was a 24/7 battle to keep it that way. And just because they couldn't say "die" doesn't mean no one ever did die.
 * Professor Farnsworth from Futurama, having been declared dead as a tax dodge some years before, found himself irritated that his son Cubert used this fact to perform a hostile takeover of Galaxy Express.


 * And of course, Leela's infamous one night stand with Zapp Brannigan is mentioned every time Zap makes an appearance in the show. Usually by Bender or, more commonly, by Zapp himself.
 * Xeexi got his Memetic Molester status by mind raping two characters in an episode. Only one instance is really ever noted, but now Xeexi is only remembered as a rapist, even though he's also a tactical genius, and well...dead.
 * Fans of My Little Pony Friendship Is Magic tend to assign traits to characters based on random memorable scenes. This includes:
 * Derpy Hooves is all about this trope. She was always depicted wall-eyed and ditzy based on a scene in Episode 1, even before it became canon in Episode 15. Her love for muffins also stems from a single scene.
 * Additionally, she is portrayed as the klutzy mail carrier based on the "Feeling Pinkie Keen" scene where it is implied that she dropped a series of objects on Twilight including an anvil and piano.
 * Fluttershy wanting to be a tree, based on a random night conversation on a train.
 * Also, fans enjoy depicting her as a Broken Bird, Cute and Psycho, or a Yandere. due to her going a little crazy in "Best Night Ever". It's probably because of the tropes Beware the Quiet Ones and Beware the Nice Ones.
 * However that wasn't the only time, since she had before this one other two (though less histerical) similar moments in "Dragonshy" and "Stare Master".
 * Scootaloo secretly being a chicken, based on a random night conversation in a forest.
 * Pinkie Pie being an insane psychopath. It was already part of Fanon due to a certain fanfic, but after the episode "Party of One" was aired, it will be hard not to think of the scene where Pinkie goes completely nuts.
 * When she's not depicted as a clinically insane Yandere, she's either a Stepford Smiler, she's bipolar, or she suffers from some sort of trauma in her past.
 * Celestia is sometimes exaggerated banishing anyone she doesn't like or would rather not deal with to the moon, all because she banished (reluctantly, even) Nightmare Moon (formerly her sister Luna - Word of God has stated they aren't the same pony, just the same body) to the moon. Once.
 * Word of God actually has stated they may very well be the same pony - one interpretation of Faust's elaborations makes it entirely possible that Luna used dark powers. But that will not be discussed here. The point is, in canon, Nightmare Moon is very very very BAD and the only person Celestia has ever banished like that. Fanon? Not so.
 * She also turned Discord to stone... after he conquered Equestria and turned it into a nightmarish World Gone Mad. Fan Dumb has warped it into a reputation of turning those who oppose her into a Sealed Evil in A Can.
 * Rainbow Dash said "twenty percent cooler" one time, so now it's her Catch Phrase.
 * In X Men Evolution, Scott was always a nice guy to everyone unless they deserved otherwise. However, Avalanche and him had a known rivalry due to being the leader of an oposing team, and usually it was Avalanche that instigated it, in fact, most if the time Scott was defending someone else or reacting to Avalanche's previous action. However, during season 2, Avalanche had changed. Not as in he developed, but his personality had completely taken a U-turn and he was suddenly in love with Kitty (Itself being a Never Live It Down moment as he'd only had one interaction with Kitty before hand and wasn't even positive) and willing to join the X-Men simply to be close. Obviously, Scott remembers how he's acted and doesn't trust him. When Avalanche proves he's not interested in learning at the institute Scott retaliates by reactivating the Danger Room control for a second to make him trip up, a complete Out-of-Character Moment that was never demonstated before or after (He made a joke, they completely forgot who this is). And when someone starts stealing the X-Vehicles, Scott, as well as EVERYONE thought it was Avalanche. When its all over, Scott apologized for this and offered to start again. Lance decides to quit because, after his time here, he's realized its too much work and not really him. However, the Brotherhood fans and a few others refuse to think of Scott as anything but a petty jerk who just hates Avalanche for no reason, who is nothing but a saintly loving Boyfriend to Kitty (Despite the fact that, by the end of this season he returns to previous characterization and breaks up with Kitty), and that Scott was the reason he quit, having driven him away with his bullying and acusations when Avalanche would have made a great adition to the team. Sigh. That's two characters remembered for a personality they didn't have, because of one episode and one Out-of-Character Moment.
 * Similarly, the New Recruits are only remembered by some fans as idiots who only want to cause trouble and if left alone would destroy the world. They only did two stupid things, steal the X-Vehicles, and break into the Danger Room unsupervised. Not only did they learn their lesson, they actually showed they were smarter than previously thought (How many of you could fly a jet or survive a Danger Room session designed for the more experienced children?), in fact, it wouldn't of been a problem had Avalanche and Kitty hadn't got in the way and caused the systems to get fried and fired at two Air force jets. But because one caused Avalanche to quit and another was 'confirmation' people always think of them as Too Dumb to Live assholes.
 * Family Guy's Brian Griffin. Some fans will never forgive him for utterly derailing the seventh season, or, for reasons that are still incomprehensible, going from a normal Christian to a rabid anti-theist after the show's Revival.
 * In-universe example: In a Robot Chicken skit on G.I. Joe, a new recruit is given the name Fumbles after slipping on his spilled soda. This leads him to defect to COBRA for the sake of revenge. Unfortunately for the Joes, "Fumbles" happens to be a Badass Bookworm Cold Sniper who is capable of single-handedly killing them all.
 * Even better, at the end of the sketch, Cobra Commander is so impressed that he wants to give the sniper a much better nickname, only for him to coldly respond "It's Fumbles. It's always been Fumbles."
 * While it's understandable since "When you wish upon a star" is basically the theme of the Disney comapny, Disney Animated Films are often generalized into only promoting that moral(that a princess, or any person just needs to want something and they'll get it). The Princess and The Frog seems to address this prevalent idea, and balanced it out with a hard work moral.
 * Benson's actions in Best Burger in the World. From mocking Mordecai and Rigby to eating their burgers, that episode turned him into The Scrappy for some fans. At first, Benson was seen as just a strict boss with low patience, but now, people see Benson as a Jerkass Bad Boss that makes Mordecai and Rigby's lives hell, despite past, present, and future Pet the Dog moments.