Which is a shame, as there are other, far more legitimate reasons to dislike him and Shagia.
Sasha Blouse from Attack on Titan really suffers from this: despite being a well-fleshed-out character with hopes and a personality, an excellent soldier, and something of a Badass, the vast majority of fan art and references have to do with her undying romantic love for potatoes. Because she was introduced by comically eating a potato. Granted, the other cadets called her "Potato Girl" for a bit, but that died down after their three years of training with her. But Jeans brings it back up again in chapter 51.
Axis Powers Hetalia has a case that's odd in that it's based on an event that hasn't even been shown in canon. As the series' characters are Anthropomorphic Personifications of nations, their characterization in fanworks are often based to some extent on real-life historical events that their representative nations, which is pretty much inevitable as it's impossible for canon alone to delve completely into the nations' histories. However, the fanon that arises from this can get rather... questionable at times, like in the case of America and Japan. One of the most well-known interactions between these two nations in real life is America's bombings of the cities Hiroshima and Nagasaki in Japan that ended World War II, and many fans take this as proof that the characters must have an angsty, difficult, and even abusive relationship (especially if they view it as a tragic romance)... even though they're shown to have become best friends in numerous post-WWII strips with not a trace of bitterness to be seen. Not to mention that in real life, America actually treated Japan pretty decently after the atomic bombings, going through its occupation of Japan with a minimum of bitterness and hostility, a portrayal that would likely fit their APH characters better.
Japan himself suffers from this. Yes, he stabbed his doting brother China In the Back for no clear reason. Yes, it was a shocking Kick the Dog moment, especially in a series that normally depicts historical events humorously, so it's understandable that it really stands out to many fans and makes them wonder about Japan's true character. And yes, many of Imperial Japan's war crimes in real life were no laughing matter. But that doesn't mean that the character Japan has to be a sociopath who ruthlessly manipulated, abused, and raped his East Asian siblings in cold blood during his imperial years, especially considering that he's shown to be on relatively civil terms with them in the post-WWII strips. And some bad acts can be undone, you know...
Spain also gets this too. Fanon likes to think he's a yandere or a Cute and Psycho because of Spanish history and Hidekaz Himaruya said in his notes that he was originally going to be a two faced character like Russia that was only kind toward Romano. Himaruya mostly discarded that idea many years ago, but decided to play upon it on the 2011 Fool's Bath where Spain seems to snap at France when he revealed who the culprit was (which was indeed Spain, who sent the threatening letters to everyone and if they didn't come to this location at a certain time, he would reveal their most embarrassing picture of them). However when Spain appears to take his anger out on America and England, he switches back to his cheery self and explains that he just wanted to hang out with everyone and France twisted the words of what he really wanted. It was obvious that his anger was because he was drunk, but the fans now declare that he is officially yandere / Cute and Psycho despite it being played for laughs.
A less extreme example would be Poland- he crossdressed all of three times in the entre webcomic, none of which were recent and one of which was deleted from the site due to Old Shame, but fandom seems to love putting him in skirts near-constantly.
A couple older strips had jokes involving Canada being unnoticeable, with only one of them making him explicitly invisible. He does not bring this up that much. In his vast majority of appearances, everyone sees him just fine, even if they occasionally think he is America (and even that only seems to really bother him when he gets beat up because of it). Recent strips, in fact, show him as being popular even; in the 2011 Halloween event all the other nations saw and recognized him just fine and cheered for him. Yet fandom still portrays Canada as the poor little nation nobody ever sees or even remembers the existence of, he is always wbhining and angsting about that (often to super-emo extents), and it's sometimes mixed with different degrees of America bashing.
Taiwan is a PluckyGenki Girl who gets along with almost everyone but China and even then she helps China when needed (though her methods are... unorthodox.) People only seem to remember that she once told China "leave Japan ALONE!" in a single-panel sketch, however, and thus they tend to believe that either she's a Clingy Jealous Girl to Japan (when she has never clung to him in the canon strips) or that she truly loathes China (when their relationship is actually much, much friendlier than it would be if Hetalia was super close to history).
Ukraine and Belarus's song Carrots and Sticks plays the Yandere archetype for laughs and makes some throw-away allusions to Ukraine possibly also loving Russia in a way similar to Bela's, only more passive-aggressively. Now some people seem to think that Ukraine is 'totally a super obsessive yandere, despite how this supposed "darker side" of her never really arises in the strips/series.
Bleach has Orihime. You get kidnapped by the Arrancar ONCE, and suddenly, you're the Princess Peach of anime. Even Kairi didn't have it this bad.
Not to mention, it just wasn't a mere kidnapping. Ichigo and the others were barely recovering after a huge battle that they lost, Orihime was trying to cope with her feelings for Ichigo and her recent depression over feeling left behind. She does fine for a bit, with Rangiku helping her to deal with her jealousy of Rukia and Rukia herself taking it upon herself to train Orihime for the fight with the Arrancar. It was only after that when Ulquiorra came with the Sadistic Choice. The radical haters of Orihime's character basically threw every insult they could at her and wanted her to die, but other sides of the fandom were disappointed that, in their view, she folded after promising to herself that she would no longer be a burden to Ichigo and fight alongside him and everyone else... (Though she ultimately managed to get out of the pit and, in the Vandereich arc, she finally got to fight alongside Ichigo and the other True Companions — without folding. Both sides either ignored it or handwaved it.)
Orihime's screams for Ichigo to help her know what to do during the climax of the Lust arc is most likely the biggest Never Live It Down moment for Orihime in the entire fandom. Say My Name is a VERY common trope in manga as a whole and Bleach isn't an exception, many other characters have also screamed each other's names at least once per chapter, and Orihime only took to screaming it repeatedly when she was having a massive meltdown. However, to a loud part of the fandom, that simply doesn't matter: Orihime can't even mutter Ichigo's name without fandom calling her "whore" and "clingy", whereas everyone else can get away with it.
A good chunk of the negativity comes from just how long she was captive.
There's a scene in the second season where Schneizel engages Lelouch in a game of chess, which became infamous all over the Internet when Schneizel moved his King next to Lelouch's, which is illegal AND impossible in chess. This tends to get portrayed as the writers being idiots who know squat about chess...ignoring that the actual game was already over and Schneizel was just testing Lelouch to see what kind of leader he is.
Lenalee from D.Gray-Man suffers from this. No matter how many Akuma she defeats, it seems she'll always be best known for that one time when she was Brought Down to Normal after a massive fight (that she did win anyway), and became unable to fight for a while. Even after she recovered from her injuries, got her powers back and curb-stomped a Level 4 Akuma, fans didn't stop portraying her as a whiny Damsel in Distress. What makes it even worse is that Allen went through the exact same thing, but nobody bashes him for it.
A similar thing happens to Dragon Ball Z, which gets often mentioned to as "that show with spiky-haired dudes". The only spiky-haired characters are Goku and Vegeta, sometimes Yamcha, Gohan and Goten, and all the aforementioned minus Yamcha plus Trunks when they're Super Saiyans. And all of these but Goku and Yamcha don't appear until halfway through the series. Not to mention most of them are related. HFIL, there are about as many "bald" characters (Krillin, Tenshinhan, Muten Roshi, Nappa, Piccolo and Frieza kinda (but then again, they're Naturally Bald aliens)... Also Vegeta's Forehead of Doom went under Memetic Mutation in Japan), but you never see this called "that show with the bald dudes". To be fair, they tend to stand out the most, but still, you'd think everyone in this show has Shonen Hair by listening to some.
Krillin is often mocked because he dies a lot. While he does die 3 times (4 counting Dragon Ball GT), there's another character who dies just as much, but never gets brought up: Chaozu. However, Krillin's first two deaths were important, memorable events that had a lot of emotional impact, the non-canon fourth one like this too, and only the third was minor (Albeit the anime made it a bit better). Chiaotzu's first two deaths were Senseless Sacrifices, and the third wasn't even pointed out, just inferred. But nobody remembers this.
Krillin's subsequent deaths are far more notable because he was revived with the Dragon Balls once already (and before they came up with new rules, the Dragon can only revive a person once). Krillin effectively cheated death twice, first by being revived and again when his friends circumvented the 1 revival rule. This may have contributed to his dying being memetic. Still, the same things could be said of Chiaotzu (As they die at about the same time; hell, Chiaotzu's second death comes well before Krillin's), but the show focuses more on Krillin so it's understandable he's remembered more.
Yamcha is often noted for dying to the Saibaman enemy's Suicide Attack, but fans often neglect to note that he was canonly taken offguard and in the manga had no time to react at all. Fans also tend to ignore that as stated in the series, Yamcha also went ahead in the fight as a favor for Krillin who had already died once and thus couldn't be revived by the Dragon Balls, instead believing Yamcha was doing it for the glory or selfish reasons (see Ron the Death Eater).
Dragon Ball Z is often poked fun at for its dragged out fight scenes... However, the only time it was really as bad as the jokes made them out to be were during the Namek Saga. Other times were not as bad.
At the end of the Saiyan Saga, Chi-Chi was completely neglectful of Goku, caring nothing for his health and only showed concern for Gohan. This is what most fans best remember for, and it leads into Accuser of the Brethren territory, as every good deed Chi-Chi does after this incident is overlooked and/or ignored in favor of this incident.
Mr. Satan has yet to live down taking credit for beating Cell. Despite him redeeming himself by helping Goku save the world from Kid Buu, fans still won’t let him live this down.
This is pretty much intentional though, since even in Toriyama's version (non-GT), he is portrayed as being all too eager to protect his inflated reputation. (as shown when he risks DEATH in a match against Trunks in a later tournament). Toriyama sort of subverted/played with this, in the final arc, the super Genki Dama is only successful due to Satan having inflated his reputation to the extent he is famous world wide as savior of the world, whereas 99.99% of Earth's population is "Goku? Who is Goku?". A case for "humility isn't always a good thing".
Goku gave Cell a Senzu Bean and threw Gohan into a fight with him, with Gohan being helpless and scared at the time. This incident is mentioned a lot when fans question his nobility and his good nature in general, ignoring all the times he protects Gohan. It's just that he thought the kid was ready when he really wasn't, not understand that Gohan wasn't the Blood Knight his father was. Goku has yet to live this down.
In the Durarara!! novels, a new character is introduced named Aoba Kuronuma. There is no official artwork of him, however he has shown up a lot in fan art. How? Because he's most remembered by being stabbed with a pen by none other than Mikado and is always drawn with a bandage on his hand. Even though he has yet to appear in the anime, jokes about what happened continues via drawings and Fanfiction.
An incredible amount of Fairy Tail fan art dedicated to Zeref has him in tears. While he did cry during one scene, he then went on to take down two of the biggest Jerkasses in the manga's history, one while giving a speech on how the man is a worthless scum who has wasted his life. The manga also spent 200 chapters throwing out occasional references to what an absolute monster he was prior to the events of the story. Much of what isn't him crying is still him clinging to Natsu and looking mournful.
Sting of the Sabertooth Guild is widely regarded as a Memetic Loser for simply surrendering at the end of the Grand Magic Games, instead of taking advantage of their weary condition as we had been led to believe he would do. This is mostly because he started off as a Smug Snake, even though he has become much more likable.
There was one instance in Fullmetal Alchemist where Colonel Mustang is seen slacking off at work and avoiding paperwork until the last second. This wasn't even a very important episode, just a little fanservice since he hadn't shown up in a while. However, try to find ONE Royai fic (or even just a fic about the colonel in general) that doesn't at least mention this 'tendency'. Just one.
Author example. Al hides a kitten in his armor once, and this is repeatedly parodied in the manga omakes (for example having an enormous cat that breaks out of the armor or multiple cats that claw Marta when she tries to hide in there, resulting in Al recovering his memory of being at the Gate).
In one of the GBA games a sidequest involves him finding and collecting dozens of cats, all of which boost the power of his special attacks where he releases a swarm of them to maul opponents.
Fushigi Yuugi as a series is prone to this. What plot? What Coming-of-Age Story? All most fans remember is Miaka and Tamahome screaming each other's names, pretty boys and attempted rape.
Miaka is only remembered as "that dumb bimbo who eats a lot and makes all the pretty boys fall in love with her". As if she never did anything else. Yui? Oh, she just went Yandere for Tamahome and tried to kill herself. Suboshi gave Amiboshi a Medicine Kiss, so obviously they're canonically doing each other. Soi sleeps with Nakago, Tasuki sets everything on fire, Chichiri says "no da", Nuriko's gay, Tomo wears makeup, let's stop here, shall we?
In Ghost Hunt, Naru is shown drinking tea maybe 3 or 4 times in 25 episodes, and other characters are often given tea as well when they come into the SPR office. The fandom, however, always portrays Naru as a tea addict. Find one fanfiction featuring Naru that does not mention tea multiple times, I dare you.
Before the Anzio OVA was released, Anchovy was shown in the manga as obsessed with victory and harsh toward Miho, which is how she's most often portrayed.
Averted with Anteater Team. They only join in the Final Battle and their sole contribution to it is being taken out almost immediately, by accidentally reversing into the path of a shot aimed at Anglerfish Team. In fan works, they typically have at least a passable understanding of how to fight, even if they're not one of the better teams.
Haruhi Suzumiya gropes Mikuru several times in early episodes and unknowingly rewrites reality once, or maybe twice. These are traits that the rest of the cast bring up a lot, and the latter shapes much of the plot even though it's not clear that it's actually happening, but it's worth remembering that she doesn't do this in every episode.
While most Higurashi: When They Cry characters can, and have, gotten past their violent reputations and their respective arcs, Shion Sonozaki is still most well-known for her acts in Meakashi. It seems like most fans don't know, or care, about the fact that her personality isn't like that. It doesn't help that Shion is Yandere, though not to the level she is when Hinamizawa Syndrome is involved.
There's also the case of Rena Ryuugu, who is perceived by many to be the series' trademark Ax-Crazy, Cute and Psycho, cleaver-wielding girl. The truth is, she is only truly like this in the sixth arc; her psychotic behavior in the first arc was merely a hallucination out of extreme paranoia by its main protagonist, under effects of the Hate Plague.
Inuyasha: Kikyo gets massive amounts of hate for her initially vengeful behavior after she was resurrected against her will, the most infamous example being when she tried to drag Inuyasha, whom she believed betrayed her shortly before she died, to hell with her. The aforementioned vengeful behavior occurred very early in the series, Kikyo only tried to drag Inuyasha to hell one single time, and she lets go of her misplaced anger towards him after discovering Naraku was behind the "betrayal" and considerably mellows out over the course of the story. But tell that to the fans who insist Kikyo is nothing but "that claypot bitchwho tries to steal Inuyasha from Kagome."
And she always tries diplomacy first. It's just that her opponents are never willing to just talk, so she has to force them to listen to her.
Ironically, the only character Defeat Means Friendship was played straight for was Fate and the only other character it was used for, if subverted, was Vita. The fandom would have you think that she beats the crap out of all of her friends despite befriending Yuuno, Chrono, Amy, Arisa (arguably not a Defeat Means Friendship), Suzuka, Hayate, among others without being locked in battle.
Interestingly enough, Dieci, whom Nanoha defeated quite easily, turned good, but the two of them have never been shown interacting after their battle.
Hayate's Cosplay Otaku Girl tendencies are also subject to a great deal of exaggeration, based off her designing the Wolkenritters' barrier jackets in a deliberate attempt to make "knight-like clothing".
Shamal's Lethal Chef tendencies tend to get exaggerated in fan works, despite Hayate suggesting in the first A's sound stage that her cooking has improved significantly and the Wolkenritter conceding that it's not as good as what Hayate makes, but it's "not bad." It doesn't help that the other Wolkenritter like to remind her about her mistakes. One suspects that the makers caught on when they included this scene◊ in The Battle of Aces.
First impressions are a large part of how a character is portrayed, and it's somewhat unfortunate that Cypha had to debut easily dispatching Signum while mocking her status as a knight. It pissed a lot of people off when it first happened, and failed to endear her to almost anyone. This can also be a positive example, though, since otherwise most fans probably wouldn't be interested in her either way now.
It's mostly remembered because it IS genuinely hilarious to see the most shy of the girls having such filthy fantasies. That and it is canon that she's got Evangeline beaten in the "Ero" charts.
This got a callback in a recent chapter, when Haruna called her and Yue "the polygamous duo".
And another in the Lotus-Eater Machine, where Nodoka's "dream" is to be with both Yue and Negi. Though to be fair, Luna/Shiori (who ships herself with Negi and Fate) and Chachamaru (who wants to go Walking the Earth with Negi and Eva) seem to have similar fantasies.
For the same reasons, nobody will probably forget Robot Girl Chachamaru's "winding" incident. It was even popular enough to get done a secondand third time. Pity how the OVA failed to translate this scene into audio-visual form.
Dozle Zabi only says "Once the Big Zam is mass produced..." once. And it's one of the most memorable lines in the series. Same applies to Ramba Ral's "This is no Zaku, boy! No Zaku!!!"
Char. One fleeting romance with Lalah, who was about 5 years younger, and an implied relationship with the slightly younger Haman and you're forever labelled a paedophile.
If you listen to the internet, Lunamaria Hawke couldn't hit the broad side of a barn if she was standing inside it because she missed a shot on a civilian shuttle moving on a relatively predictable course. On the one hand, episode 7 establishes her as a lousy shot in person when she couldn't get a bullseye at the shooting range. On the other, her ZAKU's Weapon of Choice is a long-range beam cannon...
Also, she wasn't the only person to have missed the shuttle in other Gundam shows; in an episode of Zeta Gundam, Char tried to shoot down a fleeing shuttle (carrying Jamitov), but he missed as well. Also, in the Destiny manga adaptation, Shinn, Kira, and Athrun tried to shoot down a shuttle and missed as badly.
Even Kira Yamato isn't immune. Fans seem to have clung to the idea that he's actually a poor pilot that relies on Freedom's Beam Spam abilities and only sits in the corner letting his computer do all the work. This was only true in his first battle with Freedom, in which he does indeed use full burst mode for almost the entire fight, but that's understandable because he's getting the hang of it, and the show wanted to hammer "THIS IS FREEDOM'S GIMMICK! IT HAS MANY GUNS!" into the audience. But after that he mostly sticks to sabers and his one rifle (which doesn't use the targeting computer) and in fact moves around in battle quite a bit. He never uses his Beam Spam more than once or twice per battle after that, yet the fandom seems only remember him sitting in one spot and letting his computer do all the work for the rest of Seed and all of Destiny. Of course, this probably wasn't aided by the copious use of Freedom's Full Burst attack via Stock Footage.
This is also in part because in the first part of the series, Kira pulled some tricks with the Strike Gundam that even detractors will call clever. After he gets the Freedom, this pretty much disappears in favor of the aforementioned "beat viewers over the head with the fact that Freedom has lots of guns".
Athrun has also gained a measure of infamy because he self-destructed both his suits in Mobile Suit Gundam SEED. You'd think he blew himself up more times than he did enemy mobile suits.
Nena Trinity crossed the Moral Event Horizon of the wedding shooting. Then afterwards, things got rather worse for her and she's forced to lay low, be less psychotic, helping Wang Liu Mei and when she mistreats her, Nena starts with leaking information that Liu Mei withheld to the Celestial Being, saving many lives, and when Liu Mei got even worse, Nena snapped again and killed her. While she's definitely a nutcase and generally not caring about other people's life, she's able to do both good and evil, and she's got a really tragic existence too which, while not absolving her of ANY crime, does mean she is perfectly able to be pitied. Fans only remembered that one wedding incident and think that's all Nena ever did, thereby she's an unforgivable evil little bitch.
Every member of the primary cast of Gundam Wing has at least one minor trait or famous moment that ended up being their standard fanfic portrayal. Sadly, this blatantly ignores the Character Development that sees the characters grow out of those attitudes, which in turn results in people savaging the series for having shallow, one-dimensional characters.
At the start of the series Heero is full of self-loathing and tries to atone by putting his life on the line constantly - so much so that an off-hand line of dialog ("Life comes cheap, especially mine") has become a tertiary Catch Phrase. Combined with the above, he's also portrayed as constantly trying to self-destruct his Gundam, when he only did that once in the TV series, he was facing an ultimatum to either hand over his Gundam or have the colonies' inhabitants slaughtered, and chose to Take a Third Option through Heroic Sacrifice.
He did try to kill himself two other times. First, on the beach when Relena found him in Episode 1. He fired an explosive charge in his pressure suit, but was only designed for in-space suicide by breaching the suit and evacuating its air. On the ground, it didn't even injure him. Second, in episode 3, when he at first didn't pull his parachute jumping out of the military hospital tower Duo broke him out of; he pulled it last-second, and only broke a leg.
He is not the only Wing boy who blows up or attempts to blow up his Gundam. IIRC Wu Fei attempts it first time he faces the new space model mobile suits and is outclassed, but the self destruct mechanism is broken. (manga). Nonetheless, self destructing your Gundam is firmly attached to Gundam Wing pilots... so much so that in SRW, Super Puzzle Robot minigame, the solution to one puzzle is to blow up the Wing Boys.
Relena only yelled Heero's name out loud thrice in the series (plus once more in the dub), yet people bash her as if she finished every episode with a Say My Name scream. She's also treated as a Yandere or a Stalker with a Crush despite the fact that she went to visit Heero all of once and remarked about it a few scenes laternote "I've come all the way here just to chase after a guy. Are you surprised, Father? But I couldn't help myself; I wanted to see him so badly. Can you understand how I feel, Father? Heero's the support I need to have around until I can get over my sadness over you. But he keeps running away from me...". (She did track him down a second time, but that was because she was afraid he would try to kill himself and had something she thought would convince him otherwise.)
There are also people who claim that she's constantly being kidnapped and in need of rescue, rather like Orihime later on. Relena was kidnapped all of once in the anime (Endless Waltz), but people also tend to label her imprisonment by Romefeller as a kidnapping, ignoring that it was intentional and had a positive outcome. And late in the series, she's held hostage on the space fortress Libra, but that was a snap decision by the person responsible and done while ignoring the chain of command, rather than orders by White Fang's leader to detain her.
Relena might as well get an award for this, since even the first things she ever says get this. In the first episode she asks her father to "leave yourself a little bit of free time" on his business trips, causing some to call her an Attention Whore for demanding he ignore his work to spend time with her. This ignores the fact that they are very obviously a loving family and that Relena was invited on the trip specifically so that she and her father could have some time together, only for him to have to back out due to his obligations. Not to mention that four episodes later, they go on another trip together and she takes his being busy much better.
Wu Fei is possibly the biggest victim of this in all of Wing (yes, even moreso than Relena). In an early episode he denigrates a female opponent, leading people to assume he's a psychopathic misogynist. Late in the series, he takes up the ideal of justice and becomes something of a Jerkass. It's typically ignored that there are reasons for his attitudes (Freudian Excuse, My Greatest Failure, and Values Dissonance from a strict, traditionalist Chinese upbringing), or once again that he gets over it.
Another often-cited complaint with Wu Fei is his hypocrisy, as some say his repeated statements about honor and fair fights conflict with his terroristic actions (like blowing up a dormitory full of sleeping soldiers in his debut episode). However, the show actually presents Wu Fei's internal conflict over his actions, particularly in the episode where Team Mom Sally helps pull him out of his Heroic BSOD.
The big problem with Wu Fei is that a lot of his characterization is centered around the death of his wife and how that affected his worldview. Some of you reading this just went "Wait, what? He had a wife!?" The anime never even mentions Meiran Chang, nor how her death weighs on his mind. This is only revealed in the Episode Zero manga, which goes into the pilots' backstories (it was planned to be in the anime, but got replaced by a Recap Episode due to production issues). With her taken into account, a lot of Wu Fei's more controversial actions take on a new, much more sympathetic light.
Wing even has a non-human example: The Leo mobile suit used early in the series has a reputation all over the internet (even on this Wiki) as being a shoddy piece of crap that falls apart if it's so much as breathed upon. Granted, it is a Mecha-Mook, but when not facing a Super Prototype they tend to do quite well, and are actually superior to some better-liked Gundam staples like the Zaku II when examined from a technical standpoint.
Part of this is because the Leo never got a chance to shine like the Zaku II and was never acknowledged to be a 'feat' of destroying one Leo. When the Gundam destroyed two at the same time and we saw Char using his trademark red Zaku they were thought to be feared mobile suits. Leo's? They were literal Red Shirts and never stood any chance even against other mechs in the series.
Quatre did go berserk that one time with the ZERO System, but to hear the Fan Dumb, you'd think that's normal behavior for him. He is often portrayed as mean and evil in fanfiction, even though he is neither. Worth noting, too, is that all the pilots use the ZERO System, and all of them have...issues with it. All, too, overcome them, with the exception of Duo, who lacked both the opportunity and the desire to give ZERO another try. Quatre just went more berserk (blowing up 1/3 of the L2 Colonies) because he had just had a bad argument with his dad about pacifism, and then his dad got killed.
The early dub for the anime involved a large amount of "believe it"s to cover for Naruto's peculiar speech patter n(appending "dattebayo" to his sentences). While this was reduced later on as the anime gained American popularity and eventually scrapped all together, many believe he says "believe it" every five words.
Naruto is usually seen as a Big Eater who regularly polishes off a dozen, if not dozens, of ramen bowls in one sitting. The incident that spawned this was when Naruto slugged back a dozen or so bowls while receiving a lecture from Ebisu, who was paying. While never stated, it's likely Naruto was just eating that much to screw with Ebisu.
Sasuke Uchiha's haters who claim he was always an impossibly huge Jerkass, instead of just aloof and somewhat rude - mostly in response to Naruto and Sakura genuinely irritating him (he gets worse later, but this is about how he acted at the start). For example, many are quick to cite all the times that he's put down Naruto, but forget that Naruto is the same way towards him and much louder about it. People also tend to exaggerate how many times he's told Sakura she was annoying. He said it twice. Once when she actually was being annoying, and when he barely knew her, and the other time was him joking/being sarcastic when he was about to leave Konoha and goes to Orochimaru.
Sai asked Naruto a few times when they first met if Naruto had male genitalia, as an insult no less. But from the way fans talk you'd think every other word out of Sai's mouth is penis, even as he runs around brandishing a measuring tape.
Neji was a total Jerkass to Hinata prior to his Character Development. Even after the development transpires and Neji starts very clearly treating Hinata with care, fandom still doesn't let go of his past misdeeds.
Particularly notable is the insistence that he's a "woman beater". When he fought Hinata, it was in a Chunin Exams match-up, officially moderated by jonins from the village, and she was fighting him just as hard as he was fighting her. It wasn't until she actively provoked him by pointing out the logical flaw in his beliefs (he claims destiny is inescapable, but refuses to accept his lot in life) that he tried to seriously injure her, and he was stopped by the Jonin that were watching before he could.
The fandom also tends to exaggerate Hinata's fainting spells despite the fact that she only fainted twice in the manga, (once while going into the hospital and seeing him injured, and once while he unexpectedly walks up on her when she hasn't seen him in almost three years). It doesn't help that she is more prone to fainting in the anime.
Hiashi gets this treatment. While he was negative and apathetic towards Hinata for years he learns to respect her by Shippuden. Fans will constantly portray him as an evil abusive, sometimes sexually abusive, father who wants Hinata dead or considers her completely useless.
And as for Naruto himself...y'know that "Sexy No Jutsu", an actual, honest-to-goodness ninja attack that involves turning into an alluring female (and is a regular super in the fighting games)? In the manga, he does this a couple of times in volume 1, and it's a long, long, LONG time before we see anything like it again. (Mainly because it's not a serious ninja technique, it's just a bit of goofing around, an extremely rare luxury in the world of Naruto.)
Tsunade's hitting Naruto and Jiraiya is very much exaggerated. The fandom seems to think she would hit Naruto for calling her Granny Tsunade (when it's actually an affectionate nickname) or when Jiraiya is acting overly perverted (which he doesn't do either). In the manga she never hits them except a few times such as the time she fought Naruto and that beating she gave Jiraiya when they were younger for peeping on her.
She seems to be more temperamental in the anime, as in the manga, the angriest she gets with Naruto after the Search for Tsunade Arc is raising her voice at Naruto for not showing respect to Fukasaku. Sakura suffers from the same problem. Not helped by Character Exaggeration in the anime, where one of the more forms of Padding is "Sakura beats up Naruto for no clearly defined reason."
Kakashi very often suffers from this. He invariably teaches Sasuke the Chidori and all of a sudden he plays favourites and all he wants is to train Sasuke, while hating Naruto, ignoring that teaching Sasuke this was for Sasuke's own good beyond mere strength as a ninja, and generally Kakashi plays favorites the least out of the various sensei (like Gai with Lee, Asuma with Shikamaru, or Kurenai with Hinata.)
No mention of the Accidental Kiss between Naruto and Sasuke back in episode 3? For shame.
What about Orochimaru? Bite one boy on the neck and you're labeled a molester for life.
There's plenty of things in Naruto to snark about, and a not insignificant number of them have to do with the ultimate Uchiha ninjutsu, Amaterasu. When Sasuke used it to try to capture the Eight Tails for Tobi, while it was writhing in fake agony, it accidentally hit Karin, and her coat caught fire. Sasuke's got high level reaction speeds and has complete control over his Amaterasu so he was able to extinguish it before Karin was burned, but nevertheless, it's become a meme that "Amaterasu doesn't work on people wearing black" (Team Hawk was wearing Akatsuki cloaks at the time).
Its come to the point where Amaterasu is considered to be the most useless ability given to the Mangekyo Sharingan. Detractors point out that it has never killed anyone, it burns slow enough to be removed, Killer Bee was literally faking it when he was hit by it, and its nothing more than a nuisance ( Madara even calls it a jutsu beneath his notice) by high level ninja. The hype it got in the databook was so big it would have been impossible to live up to though (Amaterasu burning hotter than the sun after all).
Also, Rei. The first episode to properly focus on her clearly establishes her as a Sugar and Ice Personality who does have emotions, but apparently, four episodes of sitting around enigmatically are enough to brand yourself as theEmotionless Girl.
Toji is known for being violent because of a fight with Shinji. Toji is normally a pacifist, and it relates to the same reason he picked a fight with Shinji: the reason he was pissed at him was how his sister was injured in an Eva battle.
Misato is often characterized as a crazy driver by fans due to a scene in the anime where she deliberately (and playfully) acted like one to give Shinji a scare.
Kaworu in the manga was introduced by strangling a kitten to death. This was never forgotten by fans.
James from Pokémon in one episode remarked that he wanted a doughnut once. In the show's earlier days, he seemed to be known for wanting doughnuts.
Same thing can be said for Pikachu and ketchup. He carried a bottle of it around for half of the episode "Showdown at Dark City" and was never seen touching the stuff again. It's still brought up in fanfics to this day, all because the scene was just too funny to forget.
One XY episode had Korrina dip Pikachu's hand into some ketchup in order to get his footprint. After she was done, Pikachu licked his hand in joy.
For the series as a whole, it was many years before Pokémon got away from its reputation of causing seizures, based on an unfortunate art decision in a single episode. Even then, the Pokémon featured in the episode (Porygon) has never appeared in the anime since, nor has its evolutions. All this despite the fact that Porygon wasn't even in the scene that caused the seizures.
Likewise Pokemon in the west has been unable to live down the reputation of things that happened during the "fad" years.
Another one for the series as a whole - the... controversial... use of a second Mewtwo in Genesect and the Legend Awakened in place of the beloved original one from Pokemon The First Movie is often believed to be a result of adhering to the Animation Age Ghetto and pandering to little kids at the almost-total alienation of the older Periphery Demographic, and is often held by these older fans as a big black mark against the series caring about them, if not the final nail in the coffin altogether.
Ash, in one episode, complained about the idea of helping Team Rocket's Pokemon because "they're the bad guys". Fanon (particularly rabid Rocketshippers) has since latched onto the idea of him being a heartless Jerkass when it comes to Team Rocket, even going out of his way to hurt them or anyone else who would help them in any way.
James crossdressed well over a dozen times but has almost completely stopped since Johto ended, and he was always Disguised in Drag. People ignore Jessie's also frequent crossdressing and act like James has Wholesome Crossdresser tendencies.
Despite all the accomplishments that Ash has done over the years, fans still think he's a great failure of a trainer because he never managed to win any qualifier tournaments. Even if more than half of those were because of something that wasn't due to his ability, like Charizard in the Kanto League or Tobias in the Sinnoh League. And of course, there's the big one: his Pikachu losing to new Trainer Trip's Snivy at the beginning of Best Wishes.
Pokémon Adventures has a reputation amongst Pokémon fans for being "edgy" and is frequently mocked for being seen as awkwardly violent and making characters into antagonists. A large portion of what people complain about - like the Arbok being cut in half or three Kanto gym leaders being made into Team Rocket members - count under Early Installment Weirdness. The series has been toned down considerably since Johto, though stuff like Norman being an Abusive Parent to Ruby and Shauna being made into a Little Miss Snarker still are relatively recent and are prime hate bait.
Did you know that Mami from Puella Magi Madoka Magica actually does more things in the series than using the Tiro Finale and getting her head eaten? Because from the way the fans talk about her, you'd think that was all she ever did. Even the official merchandise is getting in on it - a lot of it includes the Witch who killed her in some way. It also doesn't help that in the Portable game her witch form is small enough to be bite-sized.
Similarly, Hitomi Shizuki, her Muggle Best Friend and the girl who won the Love Triangle, is mostly remembered for her memetic "girls can't love girls" line. Fandom usually takes the line and uses it to turn her into a Heteronormative Crusader, or plays up her crush on Kyousuke and presents her as a Bitch in Sheep's Clothing who doesn't care at all for her friends' desires. Not helping matters is her portrayal in the Portable game.
And, of course. There's Homura. In canon, she went through hell, going through a "Groundhog Day" Loop to find a way to save Madoka. In fandom? She's a hugepervert, usually wearing Madoka's panties over her head while trying everything to molest/spy on her. It does sometimes look like she's stalking Madoka—such as when she appears outside her bedroom in the middle of the night to deliver an ominous message—but she has completely non-perverse reasons for doing so.
Even the title character doesn't get away from this. Though the circumstances of the series make it perfectly understandable, Madoka is often the least favored of the cast due to her spending much of the series standing on the sidelines and being indecisive and not knowing what Soul Gems were (never mind that Kyouko didn't know either). Some fans let it go after watching episode 10 and learning that not only was she actually a Bad Ass who leapt at the chance to be a magical girl dozens of times, but in the current timeline it's Homura who's keeping her sidelined so she doesn't recklessly lose her life again.
Thanks to the predominance of Fanon for Ranma ˝, many of the characters suffer Never Live It Down to some extent.
Akane Tendo used a mallet to hit her Jerk with a Heart of Gold fiancé twice in the anime, and only a few times in the manga... but lots of people in the manga also used mallets, including Ranma (who actually uses it more often than Akane does there), Soun, Genma, and a few oneshot characters. In fanfiction, she's the only one who's ever known to use a mallet when things get violent, despite the fact she canonically prefers her fist (and a shinai, to a lesser extent, in the anime version).
Ranma Saotome claims he Wouldn't Hit a Girl three times at most. Possibly influenced by the prevalence of the Armor-Piercing Slap, fanfic Ranma is infamous for looking down on women's combat abilities, something he never does in either version of the canon, and for refusing to strike back at women even if they're actively trying to kill him.
Please remember, too, that there's a difference between trying to kill someone and actually having a shadow of a phantom of a prayer of succeeding. Ranma doesn't go full out against Akane, Ukyo, or Shampoo because they're no threat to him. That has nothing to do with them being female either; he's just that good. And to a lesser extent Kodachi, although that was more a case of Rumiko Takahashi needing a way for that fight to last longer than 3 panels.
Shampoo once made usage of special mushrooms that made the consumer vulnerable to hypnotic suggestions, and twice tried to take advantage of a piece of love magic that fell into her hands. She didn't even plot the mushroom incident on her own in the manga, where the mushrooms were sent to her restaurant by accident (it was implied to be her idea in the anime, though). Fanfiction portraying her as a villain invariably plays up her as being a kind of "mistress of love potions and mind-controlling poisons". In canon, chemical usage is the specialty of Kodachi Kuno. And even Kodachi sticks with paralysis and sleeping powder.
There was also that incident with the memory erasing shampoo (even if it was really pressure points).
Also, according to fandom "Obstacles are for KILLING!". There were only TWO times when she either seriously said so in front Ranma and/or Akane (her first story, when she grumbles this "excuse" when Ranma begs her not to attack Akane, and during the Phoenix People story, when she actually was under More Than Mind Control and was ordered to kill Ranma) or thought so (when Taro kidnapped Akane, Shampoo quite obviously intended to kill her and lay the blame on Taro, although she never actually voiced the plan, and she fell victim to a cold water trap that the Genre Savvy Taro set to keep anyone to approach Akane). The others involved more the "I'm an Amazon and you're my love rival, so it can't be helped!" gig than trying to murder Akane bloodily just for shits and giggles or to cruelly and venomously spite Ranma for not choosing her.
Akane stopped calling Ranma "pervert" relatively early on in the manga, and when she used it again after many, many volumes of absence, the obvious Call Backmade it very funny. To the fandom, it's pretty much her Catchphrase. Though she does frequently accuse him of lecherous intentions, it's rare that she actually says "pervert".
There's one particular episode of Sailor Moon Stars where Setsuna/Sailor Pluto scares the living daylights out of the girls on about three occasions by popping up out of the blue. The girls are eating ice cream when she appears. She pops up holding a popsicle. This episode made her famous in fandom for the Stealth Hi/Bye.
Mamoru, in the anime, broke up with Usagi once, during a storyline in which he was having cryptic nightmares that Usagi would die if he didn't stay away from her. They got back together when Usagi had a nightmare too and realized what was really going on. They basically vow to Screw Destiny and fight off whatever threat comes together. During the entire storyline, Mamoru was shown privately grieving their separation and several times deigning on the Screw Destiny route himself but stopping out of fear for what would happen to Usagi. The eventual source was proven to be a future form of himself trying to test the strength of their relationship because of the powerful threats they would face from the Black Moon. The way some people (especially Seiya/Usagi fans) tell it, Mamoru despised Usagi throughout the entire series, constantly abused her or ignored her, and only got back together with her out of duty to the relationship they had in their past lives. Not even the fact that they hooked up rather fast after The Reveal completely washes it down, as he didn't exactly loathe her beforehand despite all the times he teased her.
In the DiC dub, Rei went from a Tsundere who cares deeply for Usagi despite constantly needling her in the first season to a bullying Commander ContrarianLeader Wannabe. This, plus her past romance with Mamoru/Darien, meant she was ripe for demonization by fans; some fanfics even twisted her into a vengeful harpy who would have Usagi killed just to get back into Mamoru's pants and be leader of the Senshi.
Nephrite was seen taking a drink of whiskey in episode 21 of the original anime, and had a brief, fleeting romance with the 14-year-old Naru. Fandom forever branded him as a drunk and a pedophile.
In the first season finale, the Inner Senshi all died and Usagi had to go on to fight Queen Beryl and then Metalia alone, drawing strength from her friends' spirits to keep her going. The only other season to do anything remotely similar was Stars, but from the way some fans talk about it you'd think every single big battle ended with Usagi whimpering as all her friends tuned into cannon fodder and finally using her power when their ghosts came back to pat her back. This Very Wiki has even accused her of such.
Jadeite's sexism in the 90s anime, especially in episode 13, has led a good chunk of fandom to see all of his incarnations as a raging misogynist.
Usagi's Crystal incarnation is forever treated like a pathetic selfish bitch who only wants her True Love and doesn't care about her friends despite plenty of evidence to the contrary.
The Inners are forever accused of "being desperate to find husbands by 15" because of their past life romances with the Shitennou and daring to be sad when the guys were killed. (Granted, the scene wasn't handled well, but still) There's also constant cries of "Faux Action Girl!!" over them being shown to get hurt or flattened during battles instead of curb-stomping every enemy they came across, even though in the end they always managed to pull themselves up and kick some ass anyway.
In Sekai-ichi Hatsukoi, Hatori gets a LOT of flak for what he did to his love interest (and childhood friend) Chiaki. Basically, he was stressed out from having an unrequited love for twenty years, his childhood friend was dense and his rival was rubbing it in his face that he would get Chiaki first. So what does he do that's so horrendous that that's all what people remember him for? He brutally rapes Chiaki despite him begging him to stop and being physically, mentally psychologically broken during that moment. And then he gets Karma Houdini when the two hook up later. Needless to say, mention the pairing online and the results won't be pretty.
What makes this most noticeable from other yaoi series is that Sekai Ichi Hatsukoi actively tries to avoid using rape to lead to love (making this series more realistic than some others) and so far, the three other pairings have successfully avoided it. This is the only pairing that has rape leading to a relationship, but it falls under Rape as Drama and Stockholm Syndrome. Add to the fact that Chiaki doesn't handle the situation realistically telling Hatori not to leave him instead of distancing himself like a normal person would and also not pitying Hatori during the rape scene also does not help Hatori or Chiaki's case.
Chiaki himself has a Never Live It Down moment from the above but also because of his inability to understand love. Apparently, there is a limit to how stupid you can be when it comes to romance. It's been established that Chiaki while not the sharpest tool in the shed is rather observant of certain things (like knowing Hatori's Berserk Button (since Hatori is a hard person to read) but pushing it anyway as well as knowing what his female audience wants and doesn't want when it comes to his manga along with wanting what's best for his friends and the people around him, he will always be labeled as the stupidest, most insensitive character in the series thanks to his oblivious nature and this attitude is what leads to his best friend Yanase's breakdown.
Episode 10, 15 and 16 doesn't help his cause. Episode 10, Yanase confesses to Chiaki when he's drunk. Chiaki responds by leaving him at the hot springs to run to Hatori. Episode 15, he acts like it's Yanase's fault that the previous incident happened and hits multiple Berserk Buttons in the episode. He denies that Yanase confessed to him in his head and then tells Yanase that he should hook up with one of the female assistants, effectively setting him off. End of the episode has Chiaki get Yanase's hopes up by implying that he'll think about having a relationship with him. Episode 16...Chiaki flips out at Hatori because he saw him with his ex girlfriend and goes to Yanase's place knowing full well that his best friend is in love with him and setting his expectations high. Then the rejection scene comes that leads to Yanase breaking down crying asking why he chose Hatori over him, and Chiaki can't come up with a response. Finally, Chiaki tells him that he'll see him at work tomorrow implying that he just ignored the confession a third time.
Due to the fact that Ikuto is very flirtatious with Amu, some fans think he is a playboy. He isn't, because Utau once even said that Amu was the only girl he ever loved.
Many fans of Sonic X will never forgive Chris Thorndyke for infamously taking Amy Rose's part with Shadow, despite other characters doing the exact same thing to her in other adaptions of the Sonic franchise.
Chris Throndyke in general has harmed the reputation of the anime for his tsundere attitude towards his "Sonikku", not helped in that season three kick-starts with an 18-year-old Chris building a machine to travel to Mobius just to see him despite everyone else telling him not to.
The eponymous protagonist of Space Dandy only commented on how much he liked a woman's arse rather than her boobs in the first episode. Yet, ever since then, and even after saying he doesn't think like that anymore in the following episode, he's known memetically by the fandom as an ass lover.
Kirito from Sword Art Online. It's undeniable that both the novel and the anime have Supporting Harem traits. However, the haters of the show talk about it as if Kirito was the biggest pimp in recent anime history. However, Kirito's "harem" has quite a small presence, and eventually it's more Played for Laughs than anything else. And only in a couple of few and far in between scenes.
Of course the fandom will never let Kirito live down his "Two years worth of semen" quip during the infamous sex scene in Chapter 16.5, which was confined to the site's fanfic section. Nor will they let him (or Asuna, for that matter) live down Kirito's ejaculation's "Glopping noise", either. In most hentai featuring Asuna or both of them you are pretty much guaranteed to see "glop" mentioned somewhere.
For Yu-Gi-Oh!, people who complain about shows they don't watch have always made fun of Yu-Gi-Oh! characters for having strange hair. In the original show however, only Yugi had exceptionally strange hair. The only other people who came close (like Honda and Otogi) were really no different than any traditional cartoon caricatures. Of course the later series (not made by the original creator) ran with this, and led to another lead character with strange hair in 5Ds.
Anzu/Tea is often bashed for her speeches about friendship. However, the friendship between the four protagonists is the central theme of the show aside from Duel Monsters, which was a Plot Tumor; friendship was the main original point. There's also the fact that A—this is mostly a dub-only trait of hers, she's much less preachy in the Japanese version, and B—as it is the central theme of the show, the other four give speeches about The Power of Friendship just as much as she does, especially Yami Yugi.
Mai has her skills frequently called into question because most of her on-screen duels ended as losses. Fair enough on its own, except for three things: she never went beyond recurring character status, effectively reducing the number of on-screen duels she had to begin with, the most significant duels she had were up against one of the key characters, namely either the protagonist or the arc Big Bad, and even so, she put up a strong fight each and every time and came within victory's reach.
If Zoids fanfiction were to be believed, one would think Bit and Leena were constantly stealing each other's snacks, but it's only happened maybe once or twice on the actual show.
If one only ever looked at Kill la Kill's fandom, they'd swear that all Mako Mankanshoku ever did was become president of the fight club and be in a relationship with Ira Gamagoori.
A darker example would be in the case of episode 16 of the series, which exposes the shocking twist that Life Fibres are aliens, but the moment that most people remember from this episode is the infamous "Bath Scene," which establishes that Ragyo is sexually abusing Satsuki.
TV Asahi will likely never hear the end of that one time when they censored the national anime of Japan after they partially obscured a single vacuum-induced Panty Shot in the 2013 film Doraemon: Nobita's Secret Gadget Museum ~Museum Adventure~.
Yamakan's disastrous anime Fractale not only failed to sell well but it became the new running gag for "Saving Anime Line" and torpedoed Yamakan's career and anything he touches.
The art style begins with the overly musculine Pillar Men, who wears nothing but loincloths, the rest of the series runs on flamboyant pretty boys doing weird poses on the covers, causing people to think the manga is gay when it's in fact a manly andgraphic shonen series, for this, fandom goes with the show being "the maniest gay manga ever".
Kakyoin Noriaki is a loyal companion with a sufficient Character Development, but he's mostly known for licking cherry and hunting hot moms, the later comes from him admiring Jotaro's mom once; the former is a faker's doing, with him pulling it again only as a Brick Joke at the end of the episode.