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. 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.

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 SJW, 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)
 * 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)
 * 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)
 * Timmy's parents (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')
 * 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.
 * 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 Stoch (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)
 * 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)
 * Flippy (Happy Tree Friends; received a repetitive behavior where his PTSD influenzed in almost every appearance he made. This made the moments of him killing other characters while delusional progressively boring)
 * Splendid (Happy Tree Friends; similar to Flippy, received a repetitive behavior where accidentally kills characters he rescues, often by his lack of common sense)
 * Optimus Prime (In the Michael Bay Pentalogy of Transformers, he proved he was a psychotic murderer 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)
 * 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)
 * Ren Hoek (Ren and Stimpy: Adult Party Cartoon; Same as Optimus Prime)
 * Ash Ketchum (Pokémon the Series: Sun and Moon; Proved that he is annoying as hell and proved that he would never age; Ho-Oh is still not an excuse)