Flanderization

Flanderization is the act of taking a single trait from a character and exaggerating and amplifying it more and more over time until it completely consumes the character. Most always, the trait/action becomes completely outlandish and it becomes their defining characteristic. Sitcoms and other comedy shows are usually the ones to suffer this, due to the writers doing anything they can to get a cheap laugh from the audience, even if it means sacrificing a character's personality. Either there are out of character personalities that are counted as against the characters we known in love, or there are personalities that will make you have no choice but to lose all of your respect you would have had for all the characters.

Although, flanderization doesn't always make the characters turn out awful. Some flanderization can make them more funnier and likable. It depends on how the character is flanderized.

The Simpsons, being the series which spawned this trope's very name, has this almost across the board. Over time, the series has, in many ways, become a symbol of this trope in its purest form.

In the topic of Flanderization, the American animated sitcom King of the Hill is a notable and unusual example for a series that used Flanderization. This series is unusual for giving flatter characters new aspects, then focusing on them, thus creating the sense of Flanderization at the same time as they get Character Development.

Notable victims of flanderization

 * Ned Flanders (The Simpsons; the trope namer, went from merely enjoying going to church to being obsessively religious and overly nice, and then later an obnoxiously intolerant bigot who will lash out at anyone that doesn't support Christianity)
 * Moe Szyslak (The Simpsons; became the show's punching bag, even before he was the show's punching bag, he was the main punching bag whenever he gets prank called by Bart)
 * Homer Simpson (The Simpsons; became a selfish and sometimes psychopathic moron)
 * Marge Simpson (The Simpsons; turned into an overprotective mother who's no fun at all, what is completely against her character. This happens in the episodes where the episode is disliked by fans or is just plain bad)
 * Bart Simpson (The Simpsons; turned into a borderline sociopath)
 * Lisa Simpson (The Simpsons; became a know-it-all Social Justice Warrior, which is far too against her character)
 * Maggie Simpson (The Simpsons; became a flawless Mary Sue)
 * Donald Duck (Disney Cartoons; the trope codifier; became the meanie we all know today)
 * Garfield (The Garfield Show; became an unlikable slob)
 * Jon Arbuckle (The Garfield Show; became an idiot)
 * Nermal (The Garfield Show; became a jerk)
 * Harry Potter (Harry Potter novels 5-7; became an unlikable jerk)
 * Peter Griffin (Family Guy; Became an insane, rude, selfish, and egotistical person)
 * Lois Griffin (Family Guy; Season 7-present; became a sex-crazed, abusive short-tempered wife)
 * Meg Griffin (Family Guy; Seasons 6-14; became a punching bag until Season 14)
 * Chris Griffin (Family Guy; Season 7-present; became a character going in full idiot mode)
 * Brian Griffin (Family Guy; Season 7-present; his entire personality now amounts to being a "liberal", and became a complete jerk and got even worse when he came back)
 * Glenn Quagmire (Family Guy; Season 7-present; became not just a pervert, but an implied child molester)
 * Stewie Griffin (Family Guy; went from a toddler with the mind of an evil genius to a toddler with the mind of a stereotypical gay guy)
 * In the later seasons of Arthur, Arthur went from being an average kid with an active imagination, to becoming a super serious character with almost no personality. Barely any episodes of his own show focus on him now because of this, and when they do, he often acts even more out of character. He is now often used as a voice of reason for his friends. D.W. has gotten a similar treatment, with many of her personality traits being downplayed in later episodes. The Brain went from being an incredibly smart kid who still liked things other kids did, to being someone who can't accept almost anything unrealistic. Sue Ellen went from being a tough, but friendly, kid, and the only student capable of intimidating Binky, to being someone unable to stand up for herself when bullied.
 * Spongebob Squarepants (Spongebob Squarepants; Seasons 6-8; became an obnoxiously happy moronic idiot)
 * Patrick Star (Spongebob Squarepants; Seasons 4-8; he suffered two flanderizations; he started out as kind of slow but fairly intelligent, but then around the end of the first season, he became more stupid and immature and eventually his stupidity became his main, defining trait; then, in seasons 6-8, his second flanderization started where he essentially became brain dead, with his actions becoming dangerous at times, and while Patrick had his jerky and antagonistic moments in earlier seasons, these moments pretty much became a major part of him in these seasons, and in season nine onwards, he finally got better after years of complaints from fans and critics)
 * Squidward Tentacles (Spongebob Squarepants; Seasons 6-8; became more of a butt-monkey/punching bag than he already was, with his hatred of SpongeBob and Patrick increasing to the point where it's shown a few times that he even wants him/them DEAD; his temper also shortened considerably)
 * Mr. Krabs (Spongebob Squarepants; Seasons 6-8; turned into an even bigger black-hearted and self-serving greedy monster who, in one episode, terrorized Plankton to the point where he attempted suicide (yes, seriously) and Mr. Krabs just brushed it off like it was nothing; his love for money also became over-exaggerated)
 * Phineas Flynn (Phineas and Ferb; went from being an occasionally snarky genius Everykid trying to have some fun during summer vacation to being optimism and enthusiasm personified . It's gotten to the point that if the writers want to pull some O.O.C. Is Serious Business, all they have to do is have him act mildly irritated)
 * Dr. Doofenshmirtz (Phineas and Ferb; once able to take Perry in a fight or actually pose a credible threat, gets progressively more inept and silly, barely posing any sort of challenge whatsoever. His attachment and obsession with Perry is exaggerated to the point he cannot survive a single second without him)
 * Timmy Turner (The Fairly OddParents; was portrayed as essentially a good kid in the first few seasons, who occasionally gave into his selfishness. However, he was still very likeable. However, by about the fourth or fifth season, he became a jerkass along with all the other denizens of this hellish parody of sitcom America, including his Fairy Godparents who were summoned to help him the first place. Timmy has returned to most of his original affable characterization by the sixth season onward but it still shows up every now and again, before relapsing back into it in the tenth season upon the introduction of Chloe Carmichael)
 * Cosmo (The Fairly OddParents; was originally simply The Ditz and a bit of a Cloudcuckoolander, sometimes dim but still relatively normal, and perhaps strangest of all, he and Wanda seemed to be on an equal level of airheaded and careless intelligence ("We're two halves of a whole idiot!") Starting around Season 2, he started to become increasingly dumber with each season. Now he's just The Ditz. Just look back at his character in the original Oh Yeah! Cartoons pilot — he was actually a suave and sophisticated guy, barely resembling the character he became. Also, his relationship with Wanda in Seasons 4 and 5 was the foil for a lot of marriage jokes; in a couple of episodes, he claimed to be trapped in the marriage to Wanda and that she had tricked him into it. This characteristic was toned down in Season 6, when the birth of Poof turned them into loving parents)
 * Wanda (The Fairly OddParents; was originally portrayed as being dimmer than Cosmo, believe it or not, then at around Season 1 they shared an equal amount of intelligence. From Season 2 onwards, Wanda became simply the wiser one who chastised Timmy and Cosmo whenever they did something wrong. Then, all her jokes tend to be that she's a total nag, to the point where the Barbarian Hero episode had her become the whip cracking Nagules. Her marriage to Cosmo also became one of the biggest sources of humor on the show, to the point where Cosmo made it appear that he was trapped in the marriage to Wanda; however, this was toned down in Season 6, when the birth of Poof brought them closer together and they are currently revamped as loving parents)
 * Mr. Turner and Mrs. Turner (The Fairly OddParents; they go from busy and clueless to extremely negligent parents who have hinted at times that they don't truly love Timmy, and see him as a burden. This was actually the plot catalyst in an episode guest starring the late Steve Irwin as 'The Bad Parent Hunter')
 * Sheen (Jimmy Neutron/Planet Sheen; became an immature idiot)
 * Hank Hill (King of the Hill; is known for preferring traditional things over trendy new ones. This starts to get overdone in the later seasons; case in point, "Get Your Freak Off". In this episode, Hank is more Amish than the Amish; he's almost medieval)
 * Bobby Hill (King of the Hill; in the beginning, Bobby was a late bloomer, but an otherwise ordinary kid: he was immature and impressionable, but in some ways wiser than his straitlaced family. Bobby's immaturity and impressionability eventually became the entirety of his character, to the point it's difficult to believe he was ever showing any sort of character development at all. Bobby also went from a kid who regularly watched and played sports (football, baseball, soccer and wrestling) to being so bad at, and ignorant of sports that Hank has to explain what a first down is while watching football)
 * Luanne Platter (King of the Hill; started out naive but had her moments of intelligence like being able to fix cars and know when she was being used or taken advantage of, she became increasingly ditzy in later seasons and eventually married an ugly idiotic middle aged hillbilly even though she previously stated she didn't want to marry a much older man, and after she married him she became an idiotic womanchild who acts like a five year old most of the time)
 * Many of the characters in The Amazing World of Gumball began taking rather large levels of jerkass in season 2, with Darwin being the most notable offender. On the flip side, Darwin also showed an increase in intelligence, as he was sometimes the first one to call out Gumball whenever they were doing something they weren't supposed to. He isn't as bad as he was in season 3, but he still has he moments.
 * The Annoying Orange (The High Fructose Adventures of Annoying Orange; became more annoying than he was in the web series to the point he is not funny)
 * Mayor Shelbourne (Cloudy with a Chance of Meatballs; he began taking rather large levels of jerkass in the TV show adaptation of the film)
 * Scoop (Bob the Builder; became a careless idiot in the Bob the Builder reboot)
 * Muck (Bob the Builder; became a retard in the Bob the Builder reboot)
 * Eric Cartman (South Park; became an absolute villain rather than just a jerk; not to mention, his bigotry used to be only targeted toward Kyle)
 * Stan Marsh (South Park; his maturity and intelligence over most of the adult cast has been exaggerated more in the show's run. Initially he was far more child-like and mean spirited. Compare the gang's treatment of Butters in earlier and later seasons, for example. His cynicism and aggravation at others around him was also ramped up to the point where the episodes "You're Getting Old" and "Ass Burgers" created a sharp divide with fans)
 * Kyle Broflovski (South Park; went from being the voice of reason and Cartman's contrast to a stuck-up genius prude and flak magnet, sometimes being almost as much of a Butt-Monkey as Butters. His rivalry with Cartman also increased to the point where it took up B-plots (if not the whole plot) of episodes)
 * Butters Stotch (South Park; started out as one of the "weird" kids but otherwise normal. Now he's an Unpopular Popular Character with occasional moments of brilliance. This Flanderization seems to have been slightly better received. However there are concerns that he risks becoming a Dumb Is Good character if his naïvete increases)
 * Randy Marsh (South Park; became a paranoid manchild)
 * Twilight Sparkle (My Little Pony: Friendship Is Magic; was initially a fairly lucid if prudish student who simply had poor social skills. As episodes pass, her geeky, finicky qualities are exaggerated more and more, giving her Super OCD qualities and a tendency for neurotic snit fits. Her acerbic qualities also faded, making her more naive and hammy)
 * Fluttershy (My Little Pony: Friendship Is Magic; as originally quiet and timid, but was capable of showing moments of bravery and assertiveness when the situation called for it, like when she made a dragon break down crying in "Dragonshy". Later on, she became increasingly blunt and even outright Cruel to Be Kind when it came to helping her friends or standing up for herself, like when her Brutal Honesty made Rainbow Dash's depression over Tank's hibernation worse in "Tanks for the Memories")
 * Big Macintosh (My Little Pony: Friendship Is Magic; in his first few appearances, spoke normally but also said "eeyup" a couple times, sort of as a Catch-Phrase. As time went on, Big Mac morphed into The Quiet One, only saying "eeyup" and "nope," and virtually nothing else. The few times he does articulately talk past the third season or so are treated as a big deal)
 * Yakko, Wakko, and Dot Warner ( Animaniacs ; started out as Karmic Tricksters who only torment and harm those who have been rude or cruel to them, but several of the later episodes have them bother and harm people unprovoked and be pests just for shits and giggles. One example that stands out is in "Back in Style", where they are loaned out to guest star in parodies of other cartoons and are complete jerkasses to the cartoons' main characters when their only conceivable crime is being made by studios other than Warner Bros)
 * Bloo (Foster's Home for Imaginary Friends; started out as being protective over and caring of Mac in the pilot whilst being only slightly mischievous and then became a "jerk with a heart of gold" type of character in the first season, but then eventually he lost the "heart of gold" part and just became a full-blown, straight-up, outright a-hole whose jerkiness kept getting worse and worse as the show went on until he finally started leveling off around the end of the series)
 * Brent McHale (Cloudy with a Chance of Meatballs; has the catchphrase of "Uh-oh" from his time as the mascot of the Baby Brent Sardine company. In the first film, he says it pretty often. The sequel, on the other hand, he says it so much it's reached Verbal Tic levels)
 * Earl Devereaux (Cloudy with a Chance of Meatballs; became a rude and manipulative jerk in the TV show adaption)
 * Mater (Cars; became an idiot jerk in the second film)
 * Dib Membrane (Invader Zim; was always something of the Straight Man (at least compared to Zim) but who still seemed a bit manic and gullible in early episodes. By the end he seemed far saner (though still a bit naive), as well as far less optimistic that anyone will ever believe him about Zim. Arguably counts as Character Development, however, since a lot of this would fit with his experiences fighting Zim throughout the series. As well as Dib's (an everyone else's) awareness/obsession/neurosis about the size of his head)
 * Gaz Membrane (Invader Zim; went from being a Creepy Child who would occasionally act overly-dramatically over minor inconveniences to a borderline psychopath who beats Dib up numerous times for perceived slights)
 * Lumpy (Happy Tree Friends; became a moronic jerk that enjoys torturing his friends for a living)
 * Flippy (Happy Tree Friends; became a PTSD-stricken mass murderer who kills people at the drop of a hat)
 * Splendid (Happy Tree Friends; became a brainless idiot who accidentally kills characters he rescues, often by his lack of common sense)
 * Optimus Prime (Became a psychotic killing machine in Transformers 2: Revenge of the Fallen)
 * Thomas the Tank Engine (Thomas and Friends; Seasons 9-16; Same as Spongebob Squarepants)
 * Percy The Small Engine (Thomas and Friends; Seasons 8-16; became a retarded moron like Thomas)
 * Edward The Blue Engine (Thomas and Friends; Seasons 8-16; became an old paranoid wimp who worries about everything way too much and is no fun at all, unless he is in character depending what episode it is)
 * Henry the Green Engine (Thomas and Friends; Seasons 8-16; became a paranoid coward, wimp, and a moron)
 * Gordon The Big Engine (Thomas and Friends; Seasons 8-16; became a punching bag and also a pompous killjoy, but in a bad way, even when it comes to him tempting fate or getting his comeuppance, "Bust My Buffers!" is one of the episodes where Gordon just gets tortured and Diesel, 'Arry and Bert don't get punished or scolded for their actions)
 * James The Red Engine (Thomas and Friends; Seasons 8-16; became a pretentious and complete jerk about his red paintwork without even thinking of others in the slightest, but in "James Gets a New Coat" (which was a clever episode), he gets his comeuppance for boasting about his red paint so much)
 * Toby The Tram Engine (Thomas and Friends; Seasons 8-16; same with Edward and Henry)
 * Emily The Stirling Engine (Thomas and Friends; Seasons 8-16; became a bossy, nagging, short-tempered bitch, and also turned to a really idiotic moron after episodes where we see her such a kind and friendly engine like Edward, this is an example of making your characters worse if flanderized, why flanderize them to an even worse personality? That is two flanderizations in one show! How can you make those personalities make Emily more unlikable? HiT Entertainment should have sticked to giving Emily the same personality they had in season 7, what did they do? They screwed it up, BAD!)
 * Skarloey The Little Old Engine (Thomas and Friends; Seasons 9-12; became a scaredy engine over everything, but got better in Season 16)
 * Rheneas The Gallant Old Engine (Thomas and Friends; Seasons 9-12; became a killjoy)
 * Sir Handel The Blue Engine (Thomas and Friends; Seasons 10-16; became an engine who often breaks down and also messes up sometimes, "Sir Handel in Charge" is an example of this)
 * Peter Sam The Green Engine (Thomas and Friends; Seasons 9-16; became a moron)
 * Rusty The Little Diesel (Thomas and Friends; Seasons 9-11; became too bossy to even be helpful like Emily)
 * Belle the Firefighting Engine (Thomas and Friends; Season 15; her personality was wasted in the infamous "Big Belle" episode)
 * Ren Hoek (Ren and Stimpy: Adult Party Cartoon; same as Optimus Prime)
 * Charlotte (Making Fiends; went from being a very optimistic Naïve Newcomer who tried to see the best in everything and everyone, albeit with a scant sense of logic and a few realistic dislikes every little girl would have, to a virtually indestructible Pollyanna Idiot Houdini)
 * Vendetta (Making Fiends; went from being a narcissistic card-carrying bully with supernatural abilities to a stereotypical villain who abuses the Evil Laugh and whose obsession with clams goes all the way to the name of the town)
 * Ash Ketchum (Pokémon the Series: Sun and Moon; proved that he is annoying as hell and that he will never age; Ho-Oh is still not an excuse!)
 * Son Goku (Dragon Ball GT and Super; became dumber and more manchildish)
 * Chi-Chi (Dragon Ball Z, GT and Super; became an obnoxiously overbearing mother to her sons, Gohan and Goten, to the point where she attempted to take Gohan's infant daughter away from him as she couldn't stand the thought of her becoming a Z-Fighter when she grew up)
 * Broly (Dragon Ball Z: Broly - Second Coming; became a brainless lunatic who did nothing but scream "KAKAROT!" at the top of his lungs)
 * Miho Nosaka (Yu-Gi-Oh! 1998; became a selfish, hypocritical ditz who uncaringly strings Honda around when she clearly has no interest in him and just uses him for her own personal gain)
 * Sakura Haruno (Naruto; became a violent psychopath who attacks Naruto for no reason)
 * Nick Ashby (Kate Ashby/Nick Ashby's Lawful Adventures; went from being a simply strict husband to a "heroic" jerk who kills people)
 * Sheen Estevez (Planet Sheen; Went from being a funny comic relief to an immature, childish and unfunny idiot)
 * Spike (The Tom and Jerry Show; went from being a friend to Jerry to a mean, short-tempered jerk who hates both Tom and Jerry)
 * Tommy Oliver (Power Rangers; became an annoying ranger every season after season)