Almost the whole crew of Andromeda had this happen to them after Robert Hewitt Wolfe left:
His original plan for Seamus Harper on was for him to mature and get over the constant sexual innuendos. After Wolfe was booted, the character became all about childishness and innuendos.
Dylan Hunt was a good leader, but occasionally stumped with the universe since he was frozen in time for 300 years. He was also faithful to his girlfriend. In later seasons, he can do no wrong, code violations of his position of Starship Captain mean almost nothing and he makes out with another woman every other episode at least.
Tyr Anasazi was a badass mercenary type who begrudgingly worked with, and more often than not, against Dylan to further his own schemes and the two would admit that the respective other is a highly intelligent adversary that should not ever be underestimated. Tyr eventually became a much more straight-forward (and more Obviously Evil) gun-toting brute, whose plans and schemes just weren't that impressive compared to earlier.
Trance Gemini always had some mystique surrounding her, but that point was overused to eventually culminate in viewers going "Oh, it's just another of Trance' weird plots we don't know about yet, but her future vision will make things work out anyway." Apart from that, she also mostly resigned to becoming The Medic and not having much action on-screen.
Tobias Funke began the show as a satire of "sensitive new-age dad" types, and due to his obliviousness would sometimes unwittingly end up in situations that made him appear gay; over time, that turned into a ridiculously obvious closeted homosexuality which became the crux of his personality.
Gob Bluth begins the series as a magician with no stage presence and unexceptional magic skills. But as the series progresses, his ability to do simple magic tricks diminishes more and more ("Yes, but where did the lighter fluid come from?"). Insecurity and need of his father and brother's acceptance also became ever more pronounced as the show progressed.
Lindsay Bluth in Season one would occasionally try get attention(to some ridiculous levels) if she felt like no one noticed her but was still competent and a well meaning person overall sort of mirroring Micheal as being one of the more normal people in the family. Once Season two began however, she went from mildly desperate for attention to full out Attention Whore. Her thirst for attention was Super OCD.
Lester from Beakman's World was originally a down-on-his-luck actor forced to don a rat suit and be the... ahem... Lab Rat for most of the experiments. By the end, he was a big eating obnoxious farting Jerkass who gets everything ridiculously wrong.
Sheldon started off as slightly more neurotic and less interested in socializing than Leonard, but quickly grew to where his Neat Freak and Schedule Fanatic traits were more dominant. After the introduction of Amy, Sheldon's neurotic behaviors overwhelm his intelligence, leading to Character Derailment.
Raj started off just as nerdy as the rest, his primary quirk being so shy he couldn't speak in front of women and a few jokes around him being a Funny Foreigner. His shyness and the Homoerotic Subtext in his relationships with the guys (since he rarely talks to women) eventually grew into him being Ambiguously Gay with a lot of Innocent Innuendo and very rarely is there not a joke about him being the Token Minority.
Raj's inability to speak to women except when drunk was initially just ultra-shyness, which the alcohol relieved. Later it evolved into an almost instantaneous effect - Raj would stop speaking at once (but would show no other signs of shyness), even mid-sentence , the second a woman entered the same room, but would instantly be able to speak perfectly normally on just a small amount of alcohol.
Raj's romantic awkwardness and incompetence grew as a result of this. In the early series Raj, when drunk, was far more successful romantically than either Leonard or Howard. But as the other main characters gradually settled into long-term relationships, Raj was increasingly portrayed as incompetent around women.
Bernadette, when she was first introduced, was very nice and polite, though rather ditzy. Occasionally the writers would have her say something uncharacteristically mean or violent, the joke being that because she was normally so sweet, seeing her act that way was funny. As the show went on though, these outbursts became more and more common, and the Bernadette of later seasons is a very short-tempered and competitive person. The ditzy aspect of her personality was dropped, probably to differentiate her more from Penny, and she eventually Hand Waved it by saying she initially acted dumb to make her boyfriend Howard feel smart.
The local Comic Book Store owner, Stuart, was originally just a very normal guy who successfully asked Penny out. It was a key plot point that in terms of being a decent, normal guy he was virtually identical to Leonard. While he remained a friendly guy he later gained some neurotic ticks, low self-esteem and has a lot more trouble talking to women than before. The change can probably be explained that "nice, normal guy" doesn't leave things too open for comedy and they wanted him to stand apart from Leonard.
Did you know that the American version of Big Brother used to differ from Survivor in that it was more of a social game than a competition game, and that just sociopathically pushing your way through and trying to win every competition without regards for your other houseguests would get you evicted? Or that throwing competitions was what got you further since people wouldn't perceive you as a threat? After the later seasons wherein everyone was hissing "Floater! The Load! Piggyback!" at anyone who dared throw competitions they didn't need to win or trying to play a social game moreso than a physical game...you'd be surprised. As a disgruntled fan put it,
"If I wanted to watch a Reality Game Show that was all about winning competitions with little to no social game whatsoever, I'd watch The Amazing Race."
Merton Dingle from Big Wolf on Campus went from someone who considers himself relatively handsome and talented (both academically and in the various entertainment arts) to someone with an ego the size of Texas.
Temperance Brennan from Bones went from being slightly more socially aware and somewhat sarcastic in the pilot to the caricature of smart people. She has now become considerably more socially inept, replaces ordinary words with their little-known scientific equivalents and can't spot sarcasm. This is explained as issues stemming from being abandoned as a child. Interestingly enough, even with the social issues, she has no problem getting and keeping men.
Eric Matthews went from a merely shallow, girl-crazy airhead to a Man Child. Then he became Batman, so it's ok.
Topanga, however, inverted and then reverted this. She went from hippie cuckoolander to an average normalcy in early high school. Then her intelligence and affinity to advice-giving was flanderized to make her a nagging grade-obsessed overachiever.
Corey started out as an average kid with average problems. Over the seasons, he kept getting more neurotic and wacky, to the point that he was diagnosed with hypochondriasis in Season 7.
Charles in Charge's Buddy Limbeck was an earlier example of this by the same producer (Michael Jacobs). Buddy and Eric both started out as girl-crazy guys who had no interest in academics but weren't stupid at all. As their respective series progressed, they both became progressively more stupid and eventually insane.
Brooklyn Nine-Nine has Teddy Wells: despite being a secondary character who was never really more than a Satellite Love Interest/Romantic False Lead for Amy, he's introduced in Season 1 as her perfect counterpart, whose only additional quirk is his love for pilsners. By Season 2, that's become his defining characteristic, to the point where even Amy is so bored with him she wants to end their relationship.
Anya started out a bit unskilled with human culture (and didn't even have that in her first two appearances) but got worse throughout the show. Some people believe that this was on purpose, to mess with everyone.
As both shows progressed, Angelus went from being Angel without a soul to an entirely separate entity Angel shared a body with. An evil split personality, one capable of having knowledge Angel didn't even though they were supposed to be a single mind, one whose actions depended on whether or not it had a conscience at the time.
Minor example in Burn Notice. Early episodes had a throwaway comment about Michael Westin having yogurt in his fridge. By the second season, appropriating his fridge for an op is noted as an inconvenience only because it will spoil his yogurt. Eventually, a former associate remembers Michael for being a "Yogurt Man," apparently his defining trait after conducting multiple black ops together. This was started as a bit of a Running Gag by the writers, who went to some lengths to show Westen eating yogurt Once per Episode. Supposedly, their consultant said it's full of nutrients that come in handy on stakeout.
Cliff Clavin's eccentricity and his helplessness with women. In the first few episodes, Cliff is having sex with women, including Carla's sister. Later in the series, Cliff suddenly becomes inept, and later becomes a virgin.
Carla's sociopathy goes from a good woman who is bitter to a sociopath who plays potentially lethal pranks. She softens a little in the late seasons.
Sam suffered the most post-Diane, in which he went from ex-alcoholic who womanized with women to an amoral sex fiend whose alcoholism was almost never brought up. Seems he also became a complete man-child, who couldn't be serious for even a few seconds.
Rebecca as well. At first seems to be a very respectable, and confident, business woman, who liked successful men like herself-finding Sam childish. Later when she first shows her vulnerable side with the situation with Drake, she starts to become more and more whiny about hating her life, and wanting to kill herself, acting bratty, as we hear in one episode her father still gives her an allowance, and a complete gold-digger with no self-esteem, and openly going after some guys just because they have money. The show's writers have commented that this was quite deliberate, as it was funnier, and Kirstie Alley was so good a playing a neurotic wreck.
He started out in the first season as a misanthropic, bigoted, but generally kind of harmless and pathetic Grumpy Old Man, even with occasional hints of a well-buried heart of gold. By the second season he's evolved into an overtly evil Manipulative Bastard who plays cruel mind games on his only friends and shows very little regard for anything except himself.
Justified in the season 2 finale: Pierce admits that his cynicism drives him to habitually push his friends away to test their friendship. Since the study group wasn't abandoning him, he ratcheted up his harsher traits in an attempt to push them away. His overdosing on painkillers throughout the season also can't have helped.
While his Jerk Ass tendencies were dialed back in Season 3, Season 4 saw his Racist Grandpa side flanderised again to the point of extreme bigotry. The extent of the racism caused Chevy Chase to blow up on the set and quit the show.
The Dean also progressed from being a mildly eccentric supporting character with an infatuation with Jeff, to an outrageously camp character almost constantly wearing ridiculous outfits, with his interactions with Jeff going from constantly noting Jeff's good looks to outright sexual harassment & stalking. This is even parodied several times in seasons two and three, including a montage of various costumes and a comment from him when dressed as a half man half woman that he may have gone too far.
Troy & Abed have gone from being merely being best friends, to so codependent on one another that Abed literally can't function without Troy. Individually, Troy has become dumber & more immature as the show has gone on, whilst Abed has gone from being a reasonably functioning adult to suffering a mental breakdown over his favorite TV show being delayed to mid-season.
This receives a lengthy and devastating Lampshade Hanging in the Season 5 premier, "Repilot", which addresses the show's own decline in quality and characterization.
David Platt on Coronation Street went from cheeky schoolboy to teenage tearaway to deranged, violent criminal who attempted to kill his mother, smashed up half the titular Street and went to prison. He was then released, settled with a girlfriend, and had become somewhat calmer... for a while, until he reverted back, lost his girlfriend and added stalker ex-boyfriend to the mix in the process. Later however, he has become fairly normal almost becoming a Jerk with a Heart of Gold. David wasn't exactly flanderized though, when you consider the influence of Richard Hillman at a young age would mess a lot of people up.
The Cosby Show's Denise started out as a funky, spunky, spirited, independent, intelligent young woman. Somewhere along the line, she turned into a flaky, clueless, freeloading moron. Additionally, despite being willing to leave New York travel to Africa for a photojournalism assignment (the actress was written out for maternity leave), she somehow freaked out at the notion of leaving New York, for the wilds of. . .Rhode Island.
Almost all of the characters in Criminal Minds have gone through this:
Aaron "Hotch" Hotchner was at first an intense stoic who, on the outside, was cold and distant but, underneath, was extremely empathetic, doing all he could for others (and then some) with an occasional sense of humour. Now, only the cold stoic remains. (Although this was less a case of Flanderization and more a result of the trauma conga line the character went through).
Emily Prentiss was introduced as an awkward, nerdy agent who was driven by ambition and an unparalleled work ethic. By later seasons, her personality really depended on the writer, though she was predominately cold.
Spencer Reid, though not a hard case, saw his awkwardness consume his main interactive trait. He used to be an agent who, while not the best at human interaction, could at least be competent in a social setting. Now, any social situation that's not work related is an exercise in frustration, so much so that the team seems to think it was weird when he was capable of dating.
David Rossi began as an agent who was jaded, smart-mouthed and arrogant who found it hard to adjust to the team setting. Over time, Rossi, like Prentiss, seems to have lost his defining characteristics, only serving as Plucky Comic Relief.
Derek Morgan is, without a doubt, the show's best case. When he started, he was a character who, while not as smart as Reid, could still hold his own when discussing things with him. He was also known as the team's obsessional crime expert and even worked with the bomb squad as well. He was also a sharp dresser with a keen eye for the ladies, as he was incredibly- sometimes to the point of being pushy- sympathetic. He did all this while being the team's muscle, the team's go-to guy to run and tackle escaping UnSubs. Now, all he's known for is his tough guy characteristics- you hardly ever get to see his brain in action, and only occasionally does the sympathetic side come out.
The process was eventually reversed with some of the above-mentioned characters: Hotchner became humane again and openly friendly and smiling during the arc showing him starting dating again following his wife's murder, and Rossi started filling the role of Team Dad when his character found out he was literally a father. Morgan, while still the team muscle, went with that and became a Memetic Badass.
The Banker in the US version of Deal or No Deal suffered greatly from this. He was originally portrayed as a mysterious, cold, calculating penny-pincher who wanted to buy the case for as little as possible. Through a combination of Motive Decay, turning into a Card-Carrying Villain, and repeatedly having him Kick the Dog, he was turned into a flatly evil and sadistic villain. The truly ridiculous thing about this is that he shouldn't have had anything to Flanderize in the first place. The Banker is a game official, no more, no less. It also makes the Fridge Logic more apparent: if it weren't for the banker, the players would have no offers and simply be forced to keep whatever was in the case they picked, making for an uninteresting game with no safety net. This also made the Gameplay and Story Segregation more obvious, as he became more and more unpleasant, but in the late game still offered the same deals that would put a real banker out of business, such as $550 000 for a 50/50 chance between a million and a very low amount.
The Australian version actually went the other way, originally starting as the same cheap banker. They added a feature where if someone only had a small amount in their remaining cases, and they had a partner in the audience, he would start offering them $10,000 if they guessed what was in the case correctly seemingly out of the goodness of his heart.
Degrassi does this with Sean in season 6. He became Emma's boyfriend, and just get together. The fact that he did help Ashley cheat on Jimmy in the season 1 finale is used...as the new way for them to get together. And his tendency to get angry and do marginally legal things (as if Emma didn't perjure herself to get him sent to jail afterward) were made much of.
Deb has gone through some radical Flanderization throughout the series' five season run. Originally she was tough but occasionally emotional and had a habit of sleeping around and cursing. As the series dragged on the sleeping around angle turned into a minimum of one illicit, Romantic Plot Tumor a season. Her strong emotions, which Dexter once commented she worked hard to hide, escalated to the point where she would break down and cry almost every episode. The culmination of this was a breathtakingly terrible scene in the beginning of season five in which Deb breaks down crying then fucks Quinn moments after cleaning her sister in law's blood off the floor.
Tom Matthews started out as a slightly old fashioned and sexist but basically sympathetic character to a foul mouthed misogynist, most of that behavior being triggered by LaGuerta.
Brigadier Lethbridge-Stewart was introduced in Season 5 and made a regular in Season 7, serving as an action-oriented non-scientific foil for the Doctor. Despite being a somewhat stubborn and closed-minded military man who depended upon the Doctor in dire circumstances, he was shown in his first two seasons as, if anything, extraordinarily crafty and capable. Beginning in Season 8, his most obvious traits were magnified. By Season 10, he was incapable of getting anything done when the Doctor was away, failed to understand even simple scientific principles, and was incredulous of any unusual phenomenon. This trend was reversed a little when his character was reintroduced in Season 20 after an absence of seven years.
Arguably, every incarnation of the Doctor has gone through this to one extent or another, where certain quirks and personality traits seem to become more magnified the longer any one actor stays in the role.
A prominent example is the Fourth Doctor, who, ignoring Early Installment Weirdness, began as a brooding and distant character, darker than his predecessor due to his capriciousness, foul temper and alien spookiness. He also was childish and kind and loved making his companions laugh - he wore a funny scarf and a silly hairstyle but also had a solemn, sad-eyed face whose smiles were mad and disturbing. For various reasons (Lighter and Softer direction and an Attention Whore actor) he got sillier and sillier and sillier over Seasons 14-17, becoming a total Cloud Cuckoo LanderMeta Guy known for Comical Overreacting frequent wordplay. His rakish recklessness developed into Awesome Ego. Much of the humour involved K-9 or Romana proving him wrong about something and him scrabbling to look smarter than them. A quick discussion with a casual fan of his era will prove he is more memorable as a funny Doctor with a serious side than as a serious one with a funny side, but whether or not this is an improvement will strongly depend on your own stance on Campand how funny you think Ham and Cheese mode Tom Baker is. It helped that Character Check moments would show up fairly frequently, so he still felt relatively fleshed out even though the focus was changing to his funniness. Season 18 radically Retooled his character in a differentdirection entirely and remade him into a science fiction version of Wizard Classic.
The Tenth Doctor's first appearance had him dropping an attacking Sycorax commander he had previously spared off a spaceship while saying, "No second chances, I'm that sort of man". His pacifist nature got played up more and more until he started to believe that former companions threatening to kill a ship full of Daleks who were moments away from destroying all of reality was somehow a bad thing.
The Cybermen, one of the major villains of the show, also hit several ones down the road. When initially introduced, the Cybermen were completely alien but in many ways better than humans, even winning the arguments thrown at them, and offered cyber-conversion as a choice, but couldn't care less about mankind. Later on, the Cybermen's main motto seemed to have completely become "convert everyone into Cybermen", although this could be excused by Early Installment Weirdness and the fact that their survival motive seems to be intertwined with cyber-converting. The revival series explored the heartbreaking backstory of the original Mondasian Cybermen in depth in Series 10's "World Enough and Time", emphasizing their desperation to survive their Polluted Wasteland at any cost.
In later Classic series stories the Cybermen seem to be in a weaker state due to their planet having been destroyed and the Cyberwars, which could explain their desire for more Cyber-conversion.
The second flanderization Cybermen got was the level they displayed their emotions and their weakness to gold, because it clogs their chest-units. In "Revenge of the Cybermen", the weakness was introduced and the writers and actors put much less effort in making the Cybermen seem emotionless like they originally did. When they came back in "Earthshock", their lack of emotions was little more than lip-service and they had tendency to delve into Large Ham territories, to the point it was suggested that the Cybermen remove all emotions except for rage. And in Silver Nemesis, the gold weakness was exaggerated to the point where merely being hit by a gold coin could completely destroy them.
The Daleks went from being The Grotesque, scared and reactionary towards outsiders, quietly mentioning to each other that "the escapees must be exterminated - I repeat, exterminated" and racist against their long-time enemies the Thals, to being genocidal Scary Dogmatic Aliens who scream "EX-TER-MIN-AAAATE!" all the time and racist toward everyone who isn't a Dalek. This is almost universally considered an improvement, though. What is perhaps not immediately apparent is that the first episode to use this characterization for them in full was "The Chase", which was experimenting with slapstick comedy Daleks.
A lot of the Wilderness Years Expanded Universe stuff did this intentionally, Played for Laughs. For instance, the short Christmas story "The Feast of Seven" is a poem about Doctors First through Eighth celebrating Christmas together, which is an Excuse Plot for them all being exaggerated to one glaring character flaw - the Fifth's mildness is exaggerated to the point that he thinks bringing sparkling water to a drinking party is leaning a bit on the dangerous side, the notorious tendency for the Fourth Doctor's actor to show up to work drunk and bully people on set is ported straight into the character, the Eighth's Big Damn Kiss is exaggerated to the point where he's obsessed with kissing and constantly tries to snog the other incarnations while bragging about other historical figures he kissed, the Third's fondness for wine and slight lisp turns into him showing up bladdered and thpraying everyone with saliva when he thpeaks, and the Sixth's being a bit overweight is turned to him being a Big Eater who even eats the berries on the mistletoe.
Drake just got dumber and dumber as the show progressed. At the start of the series, he was a teenager who admittedly wasn't too bright, but wasn't too dumb either. Eventually, it got to the point where he couldn't pronounce the word 'America'. As in, the country he lived in.
Megan went from just a typical mischievous younger sister occasionally pulling harmless pranks on her brothers, to a totally sadistic demon child who believes she was put on Earth to make their lives miserable. Her "pranks" also went from just simple antics like putting a bucket of water over an open door to having a full arsenal of high-tech gadgets and weapons that would make any CIA operative jealous. She also seemed to be willing to go to further extents to cause them misery; in one episode, the writers imply she was willing to put a whole crowd of people in danger of kidney failure, just so she could beat Drake and Josh in a salsa contest. Megan's case was later lampshaded in the pre-title sequence to the episode "Megan's First Kiss", where during said sequence, Drake & Josh go on a rant about how Megan's practical jokes went from childish to borderline terrorist.
The Drew Carey Show did this to several characters. Lewis and Oswald were fairly regular guys in the first season, but in later seasons they were closer to being Man Children. Mimi was introduced as a woman with questionable fashion sense who wore a (realistically) large amount of makeup, but she shortly began wearing more makeup than your average clown, and dressing like one too, Drew And Kate more or less stayed the same as they were in the first season.
Raymond started out as a relatively intelligent, if occasionally foolish Every Man whose problems mostly arose from bad luck or a misunderstanding. He was gradually Flanderized into a hopelessly moronic, insensitive wimp with very little knowledge of how to properly carry out his role as a husband and father. His laziness, selfishness and addiction to sex was elevated to a detrimental level, this resulting in him being subjected to frequent Informed Wrongness.
Debra started out as a sassy, headstrong woman, but still compassionate, thoughtful, and loving of her husband and family. As the series went on, she degenerated more and more into a jealous, bitchy, hotheaded Jerkass who actively bullied Ray, including physically attacking him.
Marie started out as the bossy, nagging, difficult-to-please grandmother of the family, but became increasingly rude, critical, smug, snobby, bad-tempered and manipulative as seasons progressed, to the point where in later seasons she almost lives to complain about, insult and humiliate Debra, and will never miss an opportunity to do so. Also, Marie was able to display moments of genuine kindness and gratitude in several earlier episodes, but these moments became significantly rarer over time. Her gradual transformation from a overbearing nuisance into a malevolently condescending bully resulted in her becoming arguably more antagonistic than Frank.
Frank's deadpan, sarcastic, and grossly insensitive antics became much more apparent as the series went on, though fans didn't seem to mind.
Robert actually was the one character who seemingly went in reverse with this trope: he started out seeming to be ambiguously autistic in Season One with some of the behavior he displayed, and the earliest episodes made initially made it seem like it was remarkable that he could function at all, much less as an NYPD officer; but as the show went on, Robbie gained more confidence and the show began to tone down his quirkiness (even as it simultaneously flanderized all the other characters, oddly enough) to the point where Robbie is a much more "together" guy by the end, though still slightly neurotic. It could possibly be explained by the fact that we learn that Season One takes place only a year after Robbie's divorce, which could explain why he's so pathologically neurotic in the early seasons (and why he's able to pull himself together as time went on).
However, one aspect of Robert that was flanderized was his jealousy of Raymond, which started out as a dry, deadpan grudge but gradually evolved into a callous, borderline psychotic loathing of his brother.
Spoofed in the Show Within a ShowWhen The Whistle Blows, where the main character, based on a person that Ricky Gervais' character Andy Millman once knew, has the catchphrase "You 'avin' a laff? Is 'e 'avin' a laff?" despite Andy's wishes to keep the phrase restricted in its use, to keep in line with the original person. In fact, much of his show involves the blatant flanderization of the various characters involved, in response to the changes BBC attempted to place on Ricky's earlier show The Office, which Extras is itself flanderising, given some of the ridiculous suggestions from BBC executives in the show being green lighted.
Maggie went from being relatively down on her luck and without social tact early in the show to being quite the sad sack towards the last few episodes.
On Family Ties, Mallory goes from a hip, wise cracking kid sister to an absolutely airheaded, fashion plate mallrat. Meanwhile, Alex goes from an ambitious go-getter (who just happens to be more conservative than his parents) to a greedy, smart ass of a jerk. In earlier episodes, the family could make a crack about Richard Nixon and Alex would barely notice but in the later episodes Alex became such an obsessive Nixon nut that he would flip out if anyone spoke badly about him. It got so bad that at one point he even owned a Nixon fan magazine complete with a smutty Nixon centerfold page. Yikes!
Season 1's "The Hidden Memory" made it clear Stark was largely Obfuscating Insanity. Oh, he still had a tenuous grip on sanity due to the torture he endured as a slave and while under Scorpius, but he pretended to be far worse to get the Peacekeeper guards to leave him alone. This was gradually forgotten upon his return, starting late into Season 2. He wasn't so crazy there, but in Season 3, he seemed to be simply completely psychotic all the time. This might be justified by Zhaan's death, which severely broke him and coincided with this portrayal. After a long absence, the end of Season 4 and "The Peacekeeper Wars" showed Stark in a far better (if still damaged) mental state.
Crichton undergoes a similar transition. He gets crazier and crazier as the show goes on. At the beginning, he seems nuts to the other crew members because of his constant pop culture references that sound like nonsense to them, as well as his extreme case of Fish out of Water. As the show goes on, possibly as a coping mechanism, he gets weirder and more outlandish, to the point where he's dancing on tabletops with a thermonuclear device strapped to himself.
FC De Kampioenen: This popular Flemish TV sitcom about an amateur soccer club started off with genuine believable characters who, as the seasons progressed turned more and more into caricatures of their personalities. After the fifth season it basically became a kids' show, with a lot of comedy aiming at the youngest members of the audience. It's no surprise that an equally succesful comic strip spin-off was made.
The best example is Markske, who was originally a medical student with a part-time job as a radio journalist. In the first seasons he was basically nothing more than a shy but smart geek, but as he became more popular he turned into a Too Dumb to Live clumsy Slapstick buffoon, specifically intended as children's entertainment.
This also applies to Dr. Frasier Crane's artsy, high society qualities, and his ignorant detachment from "the plebeians." For example, in his early seasons on Cheers he was shown watching football with his buddies. In a late episode of Frasier he didn't even know how football was played.
Frasier's flanderization on Cheers was definitely a positive example of this trope, though. When he was introduced, he was far more restrained, normal, and, well, boring than the character he became by the time Cheers ended. Since he was meant to be a one-season Romantic False Lead, his stuffiness and intellectuality was mainly used to make him seem rather dull and not someone the audience would shed tears for when Diane inevitably dumped him. Due in part to Kelsey Grammer's acting, though, he was well-liked enough to stay on past his arc with Diane, and his upper crust, pompous, snooty qualities were slowly enhanced to make him more interesting as well as making it seem that he was becoming more open and comfortable with his friends at the bar. This becomes evident in Frasier, when removed from the bar, he becomes more aristocratic (though he still is able to call people out on their crap when he gets annoyed), but when Sam or Woody visit Seattle, or when he visits the gang in Boston, he becomes a working class barfly again, which shocks Martin and Niles.
All of the main characters (except Rachel) from Friends go through this.
Joey's stupidity. When the show started he was shallow and vacuous, but was somewhat streetwise and still had witty lines and a good deal of Simple-Minded Wisdom (like pointing out to a door-to-door salesman the futility of trying to sell a $1600 encyclopaedia set to someone with patio furniture in his living room). By the end of the series, he's incapable of simple math, takes several seconds longer than anyone else to react to sudden surprises, confuses left and right, and can't even imitate sounds when trying to learn French.
Chandler's effeminacy. In the first season, he liked sports, beer, pizza and Baywatch as much as the other guys but had to fight against the popular misconception that he was gay. By the end, he has two copies of the Annie soundtrack, can identify the film Miss Congeniality through a wall, pretends to watch NFL football while openly admitting he doesn't like it, gets pedicures and has had it revealed that he (accidentally) made out with a guy in college.
Chandler's penchant for being "the funny one" also led to Flanderization; while he started out as a Deadpan Snarker, his humour instantly became more immature and puerile after a certain point (possibly when he got married). Specifically, his penchant for making jokes when he's uncomfortable gets downgraded to fart noises when he's saying goodbye to Rachel in the penultimate episode.
Watch through the series and you'll find that Chandler's childhood gets more bizarre as seasons go on. In the beginning he was mostly just traumatized over being told his parents were getting divorced on Thanksgiving, with fewer references to his dad being gay. By season nine, he assumes every kid has seen orgies by age seven, mentioned a piano teacher with wandering hands, and even took part in his dad's gay burlesque show while he was growing up.
Phoebe's quirkiness, which later manifested as an extreme dark side that turned her from a happy-go-lucky, spacey girl into a vicious, pushy woman with extreme sexual fetishes.
Rachel sort of got the opposite, she began as the Spoiled Sweet / Rich Bitch against everyone else's more subtler characterizations. At the end of the show they were all borderline stereotypes while she was the most realistic, normal person on the show.
Ross and Monica's parents were also flanderized to the point of blatant favoritism towards one of their children. It was revealed quite early in season 1 that Ross' parents favored him while putting down Monica for not doing as good as her brother or better, but the insults were much more subtle. As the show progressed, the Gellers made it very obvious that they favored Ross because of how smart he was and how he was their "miracle child" (a doctor told them that Mrs. Geller couldn't conceive a child) whereas they heavily criticized Monica for every minor flaw that she has. Her mother even forgets that Monica exists for a moment (she says she'd be left childless if Ross died) and says she's out of town when Monica wants to have lunch.
Minor recurring character Gunther started out as having a crush on Rachel and being too shy to act on his feelings. As the series went on, he was still shy, but his dialogue with the main cast when Rachel was not in earshot and his inner thoughts made him a perverted lech that wanted Rachel all to himself. It wasn't until the series finale where Gunther finally spits it out to Rachel about how he feels about her, but Rachel took it as Gunther just being cute.
Benny starts out as an annoying and insensitive Lady Drunk who still cares about her son. Later on, she starts to just be mean just to be mean.
At the beginning, George was a loving family man who only made snarky comments when the situation called for it. By the end of the series, no one is safe from his sarcasm, and he comes of as a Jerkass at times.
Katie Kanisky was always the designated blond beauty on Gimme a Break!, but this became much more stereotypical in the later seasons. When the series began, Katie was a reasonably intelligent, fairly down-to-earth young woman. However, as actress Kari Michaelsen put it, over time Katie's hair got bigger and blonder, and she got a lot dumber. Compare a first-season episode to a fifth-season episode, and it will seem like Katie lost about eighty I.Q. points.
The youngest Kanisky daughter, Samantha, also went through a dramatic personality change, although this one can probably just be chalked up to the natural process of growing up. In the first season, she was an athletic tomboy, whose interests included baseball, fishing, and schoolyard brawls. Before long, however, she started taking an interest in boys, and eventually developed into a somewhat stereotypical teenaged girl. By the later seasons, she was dressing in a very feminine fashion and was interested in hairstyles, clothes, music, and boys - above all, boys. Her original tomboyish personality was now a distant memory.
The change was somewhat less extreme than it was with her sisters, but Julie's defining characteristic - her high academic achievement - went from subtle to over-the-top as well. Early on, she was portrayed as very intelligent but also very much a teenager who still had a lot to learn and, on some level, knew it. (Quick: which of the three sisters do you think would be foolish enough to take up smoking, decades into the era when we knew it caused cancer? Now, guess which one actually did?) By season 4, nearly every line she had was devoted to either demonstrating how brilliant she was or putting someone else down for being less so.
The Golden Girls started out with four elderly women who had some reasonable character development, but over time, Rose got more and more stupid, Sophie got more and more bitchy, and Blanche turned into nothing more than a man-crazed slut. Dorothy became the straight man who insulted everyone, but despite her insults, no one ever called her out on them.
Possibly because most of the time, they were deserved. (For example, in one episode, Dorothy is trying to study for an important test, but is constantly interrupted by the other three with petty requests - would you sit there and take that?)
Good Luck Charlie - Amy Duncan started off as attention-craving and assertive mother figure. She gradually evolved in a spotlight-obsessed, 'ruling the roost' character who had other characters scared to ever cross her in any way. This in turn relegated husband Bob Duncan in to a spineless coward.
There was some backstage drama on Good Times towards the Flanderization of J. J. Evans. As the series progressed through its second and third year, Esther Rolle and John Amos, who played the Evans parents, grew increasingly disillusioned with the direction the show was taking as J.J.'s antics and stereotypically buffoonish behavior took precedence in the storylines. Rolle was rather vocal about disliking the character of J.J. in a 1975 interview with Ebony magazine:
"He's eighteen and he doesn't work. He can't read or write. He doesn't think. The show didn't start out to be that... Little by littleï¿½with the help of the artist, I suppose, because they couldn't do that to meï¿½they have made J.J. more stupid and enlarged the role. Negative images have been slipped in on us through the character of the oldest child."
Brittany started out as a stereotypical Dumb Blonde with occasional quips made at her expense. She has since been flanderized into being Too Dumb to Live, to the point that she still believes in Santa Claus and thinks babies come from the stork.
Mike and Tina suffered this as well. In the first season, Tina was a stuttering goth girl who turned out to be faking it to avoid attention but later blossomed into a skilled performer in the Glee club, while Mike was just some football jock who secretly loved dancing and later became the best dancer in the club. Their both being Asian was completely incidental. In the second season, not only did their pairing reek of Token Shipping, but they can't go five words without making some kind of reference to being Asian, to the point that Mike is referred to as "Other Asian" as often as not.
Sue suffers this in the fourth season. In the past, her over-the-top malice at least had a point nine times out of ten. She has even managed to be sympathetic at times. But now, she's just hateful and spiteful. One could contrast her two tenures as Principal: in Season Two, when Karofsky threatens Kurt she sides with the latter and suspends Karofsky (and ultimately resigns when Karofsky's allowed back in school). In Season Five, when Bree plays an elaborate and humiliating prank on Tina at the prom, she promotes Bree to head cheerleader. Even Roz Washington, something of a Jerkass herself, is disgusted by this.
Zig Zagged with Rachel. In season 1, she is characterized as a confident, assertive but sometimes demanding and diva-ish character who did have her moments of compassion and humility mixed in. In season 2, she's a complete pyschopath who nevers does something without an ulterior motive of stardom. In season 3, the writers obviously realised that wasn't working very well, and brought her back to her season 1 persona; A bit of a diva, but with a hint of sweetness and the feeling that she tries hard not to be so unlikable. Some argue they took the sweet side too far this time instead, and turned her into a boy-dependent whimp.
Quinn had a few crazy moments in season 1, sure, but for the most part she was just a misguided, intelligent girl who lost her way a bit. She was never shown to be insane. Then season 2 happened, and along with it came this trope with a dash of Aesop Amnesia. And behold, season 3, and this trope is taken up to 11, especially the plot where she schemes to steal her child back from Shelby. They forgot that as well as being misguided, that Quinn was also logical, smart, had a secret kind streak and for the most part respectable. Her only trait in the first 8 episodes of season 3 is the Misguided part, and that might not even be the word for it anymore. Moronically messed up might be more accurate.
Sam went down the same path as Brittany. He started off as a nice guy, who wasn't well-off, did bad celebrity impressions, and had dyslexia but otherwise was pretty normal. In Season Four, the writers not only ratcheted up his awkwardness (and Mister Fanservice tendencies) but made him dumb as a rock, to the point where he was barely functional. Not only did Sam become Brittany's male counterpart, the two characters even dated for several months.
In the first couple of seasons, Potsie and Ralph were actually somewhat sharper and more worldly than Richie. They soon devolved into a hopeless ditz and a compulsive lame jokester, respectively.
Speaking of whom, in the first season, Potsie and Richie were the best buddies and Ralph was in their circle of friends but decidedly less close to them than they were to each other. Richie and Ralph more or less switched places afterward.
Matt Parkman's power was initially simply the ability to read minds. As the series went on, this was gradually expanded to the point of anything to do with minds.
Ditto Tracy Strauss - initially can just turn people into ice, but later expands into practically anything involving water.
Subverted with Sylar. In Volumes 1 and 2, all he wants to do is kill people in order to gain their abilities, and he cares about absolutely nothing else. While this is never removed, its importance is gradually reduced, as Sylar remains evil but for increasingly important other reasons.
Dr. Lisa Cuddy underwent this kind of treatment. In season two, she was taking fertility meds to get a baby. As seasons progressed, her baby obsession became worse and worse, until she turned into a weepy wannabe mom whose biggest ambition in life was to bring up a kid. House himself is also Flanderized, with his drug abuse and fervent atheism becoming more pronounced over time.
If you watch all the eight seasons and then watch the first episodes of the first season again, the contrast is quite pronounced. House is basically not a jerk, he does not constantly meddle with the lives of his team and Wilson, and basically the only thing he does is to bicker with Cuddy. Your mileage may vary on whether this is character development or flanderization.
Robin was always meant to be a strange mixture of tomboy and girly-girl, but she gradually lost a lot of innate feminine qualities and became very jealous if someone showed a new girl more attention than her.
Lily had a little Team Mom qualities and was very physically passionate with Marshall. Both gradually consumed her character, to the point it was revealed she was responsible for many of Ted's break-ups because she knew they weren't right for each other.
Barney's womanizing ways were always to the extreme, which varied from episode to episode depending on the success rate. While it is hard to exaggerate an already wacky character, more episodes in the fifth season were dedicated to him looking to score, including putting up a big sign at the Superbowl that gives him hundreds of calls in "Rabbit or Duck," explaining his elaborate schemes in "The Playbook" and "The Perfect Week" where he goes 7 for 7.
Ted started out as a slightly dorky (but still often charming), hopeless romantic with a few pretentious, hammy qualities. The pretentious side became exaggerated (such as in "Wrestlers vs. Robots") and his hammy qualities also overwhelmed his romantic side.
It seems that Season 6's main purpose was to reverse as much of this damage as possible - and the characters in Season 7 seem much more in line with what they were in the first four seasons.
Sam's tomboyish vibes from Season 1 evolved into various examples of extreme bullying, anti-social and sociopathic behaviour, like her running a child labour sweatshop in Season 4. After that season the writers knew they were going to have Sam continue in the Sam & CatSpin-Off, and attempted to de-flanderize her. YMMV on how much that worked, but they have definitely toned her down for the actual Sam & Cat show.
Not much of an improvement if at all. Her apathetic and glutinous characteristics were then flanderized instead and she became more unlikable than ever.
A minor character, Officer Carl, went through this. In his first appearance, he was a fair minded police officer who arrested Spencer for causing a huge traffic jam and understandably got mad at him for putting up a sign that said Pee On Carl. Spencer apologizes and explains it was an accident, he even had video proof it was an accident. In later appearances on iCarly.com and the show, he is shown to be a corrupt officer. He still holds a grudge against Spencer for putting up that sign, despite Spencer pointing out he got revenge on him for the by using humiliation as a punishment for an unrelated offense. He also refused to arrest photographers who committed vandalism because they took pictures of his daughter's rabbit no charge. He then gives Carly a ticket for having a car with no license plate, and doesn't nullify the ticket when Carly explains to him the car is a prop.
Season 5 is horrible for this:
Carly has started randomly insulting people, telling off Spencer and being mean spirited.
Freddie has started dismissing Carly, ignoring her, blowing her off and generally treating her like shit.
Sam's antagonism and fighting with Freddie was blown up in both iDate Sam & Freddie and iCan't Take It. While she has screwed with Freddie in the past, in iCan't Take It, she sabotages Freddie's science camp simply because he didn't know what time it was when she asked him.
Her mistreatment towards Cat or any of the kids they watched in the spinoff was just as despicable.
Also Carly has become dumber. While she was never Lisa Simpson, she was a good student at the very least, She complained about not getting a well-deserved A in a class. As well as being generally pretty smart, she also worked hard on her schooling to get her first ever straight a's. She was also much more book smart than Sam to the point where she was accepted into a private school that even Freddie wasn't. But now she seems just barely smart enough to live. This didn't happen all at once, but gradually over time, coming to a head in season 5. Like in the space episode, she can't pronounce claustrophobic, even though she is claustrophobic. In iQ she has to fake/cheat being intelligent to try and impress a guy when the old Carly would've have been able to at least hold the conversation easily.
Dee starts out as the level-headed voice of reason of the group, but her insecurity gets flanderized in later seasons to make her just as shrill, mean and pathetic as the guys. Some of this was at the insistence of the actress.
Dennis goes from a shallow, preppy casanova to a sexual predator, borderline rapist and sociopath.
Dennis: 'Cause if the girl said no, then the answer obviously is no. The thing is that she's not gonna say no, she'd never say no ... because of the implication.
Frank goes from a successful businessman to a total wreck. This is an in-universe example, as Frank states in his very first episode that he wants to leave his respectable life behind to scheme and scratch through life in the dirt like the rest of the gang. His physical appearance also deteriorates in each season.
Mac is very interested in muscles and karate, which is increasingly played for its homoerotic undertones to the point that Mac becomes Ambiguously Gay.
By season nine it's arguably not even ambiguous anymore, as in "Mac Day" he delivers a lecture on the evils of homosexuality and attends a male bodybuilding competition in order to oil up the participants... and does both with a full-on erection.
In the first couple seasons of Judge Judy, Judy Sheindlin was a fairly reserved judge who rarely (if ever) yelled or lost her temper, and spoke in a lower tone. Come the later seasons, the popularity of her scathing wit meant that she won't hesitate to shout (and, on some occasions, threaten to throw out) anyone who doesn't follow the rules, and is easily prone to outbursts or rants at the plaintiff/defendant. These days, she seems more intent on making herself out to be a bitch than making a solid or sensible ruling. Byrd (her bailiff) used to be the near-silent right-hand man, but now he's almost guaranteed to get a moment or two of wry humor in each case, and it's not uncommon to see Judy and Byrd joking with each other in any given episode.
Kamen Rider Fourze's Yuki was initially a bubbly, hyper, yet smart and thoughtful girl whose grades were almost as good as Kengo's and could impress Chairman Gamou (a former astronaut) with her knowledge of space. This is exaggerated through the series until she becomes an increasingly loud, screechy, childish nuisance who literally believes in imaginary "rocket gods". At peak Flanderization in the Aquarius two-parter, plenty of viewers had gotten so sick of Yuki that they wanted her kicked out of the Kamen Rider Club and replaced by the Monster of the Week, who likewise despises Yuki for treating space exploration like a joke. She gets a bit better in the Gemini two-parter, where Yuki almost gets replaced by an Evil Twin, with even her own friends mistrusting her, but for many fans the damage had already been done.
It happens to Gentaro in the movies. During the show, his goal is to befriend everyone at school. This trait is taken Up to Eleven in the movies where he's befriended sentient space goo and a giant, sentient space station.
Likewise, while Gentaro has a fair number of Catch Phrasesnote "UCHUU KITAAAA~!", "Kamen Rider Fourze! Let's do this man-to-man!" and "I'm the man who will befriend everyone, Gentaro Kisaragi!", he was still a well-rounded character. But any time Fourze re-appears in crossover movies and such (especially after Souta Fukushi moved on to other projects), his dialog is 99% those three Catch Phrases repeated endlessly (or variations thereof), and Toei seemingly casts Fake Shemps based off their ability to shout "KITAAAA~!" as loudly as possible rather than actually sounding like Fukushi.
The Canadian television series Kenny vs. Spenny involves two roommates in a house competing against each other in a series of tests to find out who is better at certain things. In the first season, it was very tame (little to no profanity or crude references) and both hosts maintained a relatively civil (and even positive) friendship with each other, even when one or the other lost the competition. When the show moved to the Showcase Television network, both characters' personalities became exaggerated. Kenny went from "mildly entertained by rigging the contest, but still a good friend" to "unrepentant Jerkass who spends most of his time thinking up the next borderline-illegal plan he can use to win a competition". Spenny went from "amicable straight guy who won't stoop to his friend's level" to "meek nerd who pretends he's mature, but suffers from severe paranoia and whines about everything."
Happened to virtually the entire cast of the French Canadian show Le Cœur a ses Raisons as the show moved further away from being a parody of American soaps and more toward comedic absurdity: Ashley started out as a slightly ditzy nurse, and later became a few steps away from mentally disabled. Criquette began as spoiled and melodramatic and became downright hysterical about the slightest things later on ("You left the toilet seat up! This proves you have a mistress!").
Harriet Oleson started out as a bitchy and irritating business woman who antagonized the Ingalls family. By the end of the show's long run, Harriet had evolved into the butt monkey who was always on the wrong side of a conflict and could never win.
Charles started out as a hard-working family man who turned into a man who was destined to fail at nearly everything he attempted.
In Lost, Sayid's role in season 5 was to contemplate his past crimes, then commit some more so he can contemplate those crimes too. Season 6 "rectified" this by killing off Sayid and reviving him as a infected Sayid who literally can do nothing but kill (which came with some nasty Unfortunate Implications). They attempted to justify this in story when Sayid was revived. He was taken over by The Man in Black's "sickness" and thus was consumed by evil. Claire showed the same sickness while serving the Man in Black. The problem was, this ended up more like an Informed Flaw, as there was never any proof that the sickness even existed at all, let alone what it actually did, since both Sayid and Claire ultimately chose to be good of their own free will.
The title character of MacGyver originally started out as a reasonably intelligent, inventive field agent who lives a fairly clean, active lifestyle and was generally a nice guy all around. As the series progressed, his inventiveness started warping reality to facilitate it (although, due to the series also phasing the improvisational inventions out at the same time, this probably started happening because they needed to make sure that one aspect counts each time it gets used), his clean living became almost pseudo-hippie, and him being a nice guy somehow mutated into being the only refuge of sanity who has to deliver AnviliciousAesops by the truckload. By the last two seasons, he was pretty much just a shell for which the writers could insert their filibusters.
From Malcolm in the Middle, Malcolm became a more whiny jerk, which is justified because he was going through puberty. Also Lois went from a hair triggered tempered parent who uses Tough Love to keep her boys in line to a borderline-psychopath living vicariously through the only son who's smart enough to succeed in the world (Malcolm) as shown in some later episodes.
Kelly Bundy's stupidity (she was originally merely Book Dumb), along with Bud's geekiness. The latter ended up being a blessing in disguise when it led to actual intelligence, making him one of the few successful Bundys.
Not to mention Kelly's promiscuity. In the first season, she was somewhat rebellious, her having a new boyfriend every week (and the delinquency of said boyfriends) just another way of showing how rebellious she was. By early second season, she was officially the school slut, and started dressing to match. By the third season her regular street clothes (and school clothes) were the epitome of Stripperiffic, and by the time the show was over, she was such a slut that she would cheat on a guy if he so much as left her alone for a few minutes, and so dumb that the only way she could get out of a frat house was by shouting, "I'm pregnant!"
Marcy goes from a moderate feminist with a disliking of Al and the occasional hint of psychosis into a full-blown misandrist Sitcom Arch-Nemesis who will take action solely to make Al and/or men in general miserable. This might even fall under Fridge Brilliance as this only started happening after her husband Steve left her. Then again, living next to Al Bundy for several years might do that to anyone.
This applies to all the characters in general. However, their exaggerated, cartoony personalities are generally seen by many of the show's fans as more entertaining than their subtler, more down-to-earth versions.
Bud, Bud, Bud, Bud.. We could go on for hours how much his sister suffered from this, but he gets hit pretty hard with this as well. At the beginning of the show, he was the Cool Loser who could outwit (and outdo) his sister and wasn't as victimized by her and the rest of the family. Then around season four, his quirkiness that still attracted girls turned to outright nerdiness that they gradually rejected and it was portrayed that no matter how many times he had sex, no matter how attractive David Faustino became, he was still a virgin. Even worse, his reputation for being a pervert overtook his other qualities, that he was seen as someone who had to pleasure himself because he apparently was so lonely and repulsive to women (or at least according to Kelly), from doing it in a public library to the one apparent flashbacknote Which is also the one where Kelly supposedly ended up stupid due to hitting her head in the car as a child where he was caught doing it as a baby.
Corporal Walter "Radar" O'Reilly grew more and more infantile as the series progressed (while, ironically, actor Gary Burghoff's hair grew thinner and thinner). In the early seasons, Radar, while certainly young and inexperienced, wasn't a total innocent; he drank, played poker with the guys, helped himself to Colonel Blake's cigars, and was clearly a sly and knowing individual. In later seasons he became so childlike that he drank nothing but grape soda and couldn't say words like "nudity" without stammering. Additionally, his literal telepathy — demonstrated in more than one early episode — eventually degraded to simply an ability to hear incoming helicopters before anyone else, a feat which Hawkeye was able to duplicate during his Temporary Blindness.
Radar's turnover happened early in the first season; around the same time Ugly John and Spearchucker left the series.
Subverted with Corporal (later Sergeant) Max Klinger, who slowly lets up at his attempts to get out of the army as a crossdresser. He comes up with some pretty creative alternatives, however, including attempting to eat a jeep, threatening to set himself on fire, and pretending that he's seeing the camp as Toledo, Ohio (Jamie Farr's hometown). To counterract this he becomes progressively dumber as the series goes on.
Frank Burns started out as a sanctimonious, hypocritical Bible-basher who spouted off on the sanctity of marriage while engaged in an adulterous relationship with Margaret Houlihan. He went from that sober, unremarkable (and somewhat boring) character to a manic paranoid hebephrenic moron (with a side order of John Birch-esque jingoism) within just a few episodes.
Hawkeye also suffers from this. He starts out as a quasi-adolescent, heavy-drinking, womanizing, war-protesting draftee. In later seasons, he's something of a patriarch to whom even the chaplain goes for advice.
Colonel Potter's crankiness seemed to get more severe with each passing season. Although anyone would be cranky having to manage that cast...
Merlin used to be quite good at hiding his magical abilities by rationalizing (or completely avoiding) the odd situations he often found himself in because of them. Nowadays not an episode will go by that doesn't have Merlin getting caught in compromising positions (usually with a dose of subtext), and having to explain himself with increasingly bizarre excuses. By this stage, Arthur thinks that he's an alcoholic weak-bladdered cross-dresser who prowls around the castle at night, is obsessed with pest infestations, and has serious mental problems.
Arthur started out as an arrogant prat, but he was also observant, intelligent and quick-thinking, and wasn't afraid to defy his father. In later seasons, he was given crippling Daddy Issues, would dismiss Merlin at every opportunity, and was utterly oblivious to magic even when it was happening right before his eyes. To add insult to injury, it became a Running Gag that he wasn't even able to dress himself. It's actually quite shocking to go back and watch him in the first seasons, in which he immediately takes Merlin's word that a magic-user is on the loose in the second episode, and for him to correctly identify a small hurricane as magical in the tenth.
Adrian Monk. He went from having an (admittedly rather severe) case of OCD but still being very good at his job to accusing someone of murder just because he was a nudist (though he had a Freudian Excuse) and being unable to perform simple tasks. For example, in Season 1 we're told that Monk wasn't reinstated because Stottlemeyer withheld his recommendation. In Season 3 all he has to do is complete a multiple-choice test. He physically couldn't complete the test (however, all kinds of OCD become more pronounced under extreme stress). His neuroses start small, before slowly getting Flanderized to be worse and worse, until the problem is no longer that his wife's death broke him (as was the original justification for him turning in his badge), as they became retconned into not only his past, but his family as well. This is most notable at the end of the series, when he is reinstated, because he shows a level of incompetence beyond his neuroses, making it impossible that he was ever a cop to begin with.
Even worse, Randy Disher. Went from being a slight Cloud Cuckoolander who tried to solve cases by copying everything Monk said, into somewhat of an ADHD-kid like guy who by the series finale we wonder why the hell he lands a job as a police chief as he hasn't contributed much as far as the series is concerned.
This has happened to several characters from The Muppet Show when they made the transition to the movies.
The biggest example would be Statler and Waldorf. In the original show they were audience members who constantly complained about the show. They show up in various roles later, where they complain about everything and seem to have never had a positive experience in their lives. A lot of people still love them because of this. Statler and Waldorf get another case, because while they complained a lot during the show, they didn't complain about everything. Indeed, when it came to classic vaudeville numbers, they were positively enthusiastic and would even sing along, and rarely had anything negative to say about the guest stars. Fast forward a bit...
Sam the Eagle got it too. Originally his Eagleland obsession came second to his Moral Guardianity, but over time the former trait exploded out of control.
Even Miss Piggy, who was always considered one of the more three-dimensional characters in the Muppet canon, fell victim to this. In many of her appearances in the 2000's, her karate-chopping schtick has been overused and her negative traits and attitude problems have been over-emphasized. The 2011 movie did revive her original Jerk with a Heart of Gold personality, though.
Kermit the Frog's personality from the late 60s specials was that of a major wise-ass, which eventually mellowed and morphed into an sarcastic, high-strung everyman who just barely managed to hold the show (and often, himself) together during The Muppet Show's run. The Muppet Movie took the everyman part of his character and added his characteristic "daydream believer" side. Several years down the line, Kermit has essentially become the Muppet version of Mickey Mouse (who, ironically enough, ALSO got flanderized into a very flat character), a generally likable but very bland character.
MST3K's Professor Bobo, introduced in the eighth season, started as a slightly dim but basically competent Planet of the Apes spoof who chastises his colleagues for their simian behavior (while occasionally indulging it himself). Over his run he became progressively more idiotic and bestial. Likewise, when first introduced (also in the eighth season), the Observers are kind-of-omnipotent, maybe-not-really-superior beings. Within a few episodes, Brain Guy is just a super-powerful bozo who can't give a countdown without losing his place. Note that their boss was the utterly terrifying and thoroughly emasculating Pearl Forrester. Maybe she just has that effect on minions.
In The Nanny, Sylvia was caricaturish to begin with, but during the later seasons her whole character was reduced to two running gags: her grotesque overeating, and her obsession with her daughter Fran getting married.
Missy went from a normal Alpha Bitch who wasn't even interested in Ned, to a persistent, manipulative psychotic Stalker With a Crush who's dangerously obsessed with him.
Moze begins as a normal (yet kinda obsessive) tomboy who was okay at sports and hated being girly. In season 2, she's perfect at every manly anything, but also considered hot by guys even a grade higher than her.
Cookie was originally Ned's nerdy best friend that more often than not got into trouble with him. In the final season of the show, Cookie would almost always have a plan to score with Lisa Zeemo, a nerdy girl that turned out to be Beautiful All Along. He and Ned very rarely did anything together, and attempting to date Lisa became his only other character trait.
Just about all of the characters on NewsRadio became increasingly offbeat as time passed, but Lisa Miller seemed to stand out as the one who REALLY became wacky, compared to what she was like originally. When the series started, Lisa was a fairly level-headed, down-to-earth journalist who often seemed to be the designated "rational one," keeping the station going in the face of Dave's inexperience and the other characters' eccentricities. Over time, Lisa's neuroses became more and more pronounced, such as when she decided to re-take the SAT to see if she was really getting dumber, and when she revealed that her obsession with academics had led her to gain an extensive criminal record (stealing a car because she was late for an exam, breaking into a post office to get her college admission letters). By the final season, she had lost all connection with reality and basically turned into a cartoon character. Her crowning moment of insanity had to be when she chose to go through with her wedding to a convicted criminal because, as she decided, having a husband in prison was a great way to balance marriage and a career.
You'd be hard-pressed to find a character from Night Court who wasn't Flanderized.
Dan Fielding started out as a relatively straitlaced prosecutor, but quickly turned into the narcissistic, skirt-chasingfaux-jerk we know and love.
Bull Shannon started off as a menacing yet deep character, eventually morphing into a totally harmless, child-like clod.
Harry started off as a somewhat goofy, but well-meaning judge who enjoyed performing magic tricks. Fast forward a few seasons, and he's much more of a Man Child (one character has to check to make sure he didn't get his license from a Cracker Jack box), and his love of Mel Torme has exploded into full on Stalker Without a Crush.
Pretty much everyone on the American version of The Office, but Michael is the most prominent example, going from being an obnoxious boss who really did mean well to being a total spaz who couldn't handle being shown up.
Jan went from being the Straight Man and voice of reason to Michael to a mean spirited loser in record time after they officially began a relationship.
Jim may be a subversion. In the first three seasons his love of pranking is a defining character trait, and this trait would normally be Flanderized to hell and end up with ridiculously elaborate and frequent pranks. However, in Season 4 the number of pranks he does drops to seven from the previous season's twenty-four, and in Season Five he pulls the same amount, despite the season being almost twice as long as the previous one.
Ryan started out as a shy temp, lacking in confidence and largely passive. He worked his way up to sales and continued to lack confidence that is until he was promoted to Vice President. At that point he started to act like a bit of a hot shot. He proceeded to sabotage his own career by misleading shareholders and went to prison. Through a series of misadventures he ended up back in his temp job at Dunder Mifflin. The odd thing is upon returning the newfound confidence he had from being VP didn't go away, in fact it only became stronger. He now acts like a complete arrogant self important ass. He constantly citing his brief stint as an executive in New York as a reason he's an expert in everything from stage makeup to the mafia.
Most of the characters on the show have undergone this to some degree. Kevin Took a Level in Dumbass and prioritizes eating over absolutely everything. Kelly has gone from being slightly immature and air-headed to having loud, dramatic emotional outbursts on a frequent basis. Meredith went from a boring accountant, to a woman with some alcohol issues, to a complete wreck. Creed's occasionally-hinted-at shady past has been gradually built upon to the point where he appears to be some sort of criminal mastermind. And Dwight went from being an obnoxious, arrogant over-achiever with a rigid ethical code to a ruthless, back-stabbing corporate shark who cared only about self-advancement and the humiliation of his enemies, with a healthy dash of paranoid Man Child thrown in, to boot.
Toby's apathy was amplified several times later in the series as well as his unsuccessful personal life. Even though Oscar was smart, he wasn't always on the edge of his seat to point out a flaw in someone's logic, now he's a pretentious smart ass. Phyllis went from being a sweet older woman who had low self esteem to a Bitch in Sheep's Clothing.
Trigger of Only Fools and Horses started out as merely a bit slow and a bit dim - he called Rodney Dave, he could be caught out in negotiations, he was socially awkward etc - really basic stuff. He was also considered by those who knew him as a man that you shouldn't mess with; in the Frog's Legacy even Boycie backed off when Rodney cracked a rude joke about Trigger's aunt Rene. By the end of the final Christmas trilogy he had become so dumb that he was literally confused by his own blinking.
Mark Brendanawicz was hit with what might be described as de-flanderization. He started off the show as The Casanova whom Leslie was crushing on, but while the other characters developed their own shticks, Mark's defining character traits fell by the wayside, Leslie got over him, and he ended up being a Straight Man. He was Put on a Bus at the end of the second season.
Tom Haverford's over-the-top, attention-whoring, obsessively entrepreneurial traits were massively enhanced in early season 4 with the "Entertainment 720" arc. However, ever since the company went bankrupt, he appears to have gone back to his earlier personality again. Perhaps it was just Jean Ralphio's influence on him.
Chris Traeger starts out as an ultra-positive borderline Ace who has trouble dealing with negative situations. The latter part becomes more pronounced over time, making him into a Broken AceStepford Smiler who ineffectually hides his depression.
Initially, the fact that Ben liked calzones was just a part of his status as a Fish out of Water from the "big city", as people in small town Pawnee like pizza and have an irrational aversion to calzones. Later on, the dish becomes something of a Trademark Favorite Food for Ben, and in one episode, a depressed and somewhat irrational Ben becomes obsessed with the idea of opening up a fast food calzone restaurant.
Jerry's status as the department's Butt-Monkey grows with each season.
In early series, the others get his name wrong simply through genuine belief that "Jerry" is his real name. By Season 6, they are openly and deliberately calling him by the wrong name.
Up to about Season 5, the other characters are on occasion shamed by Leslie and Ann into feeling guilty about how they treat Jerry. When Ben tries the same thing in Season 6, he is shouted down by everyone.
Ron's flanderization really started to show in the last half of the series. He always had a distaste for bureaucracy while valuing privacy and self-reliance. But his simple and straightforward tendencies have been reduced to writing once sentence on his will; and now overreacts when he has to abide by anything "official" or when he gets asked anything about himself. He will go unnecessary lengths to maintain those views.
Andy goes from a lazy, only somewhat stupid Man Child as Ann's boyfriend to a lovable oaf who is borderline Too Dumb to Live.
Lt Frank Drebin of Police Squad! In the TV series, he was a competent police officer by the standards of the world in which he lived (a world in which Abraham Lincoln survived his assassination by being a badass and the shoe shine boy is over 50 and an expert on theology and medical procedures among other things). By The Naked Gun series, he became a Clouseau-like incompetent whose clumsiness was in-universe.
Bob Barker's hosting style slid from "amicable, with a dry wit" to "Deadpan Snarker" to "cranky old curmudgeon" over the course of 35 years.
Rich Fields, who was the announcer from 2004 to 2010, became much, much louder. By the end of his tenure, he was practically screaming half the time ("A NEW CAAAAAAHHH!!").
Psych. Where do we begin? Shawn went from being a happy-go-lucky average-intelligence charmer to a genuinely stupid, somehow universally attractive, lovable asshole, while poor Gus went from Shawn's slightly uptight but more traditionally competent and knowledgeable buddy to a total loser whose areas of expertise are mostly informed abilities and exists almost solely to finish Shawn's pop cultural references. Jules went from being your average cop stand-in with a little bit of UST with Shawn to The Chick, and Lassiter went from being Shawn's Foil with a little bit of hidden bigotry to such a gigantic creep that it is honestly a wonder why anyone lets the man near them. Buzz McNab (Ensemble Dark Horse, anyone?), meanwhile, has all but disappeared. He's mostly rescinded back to his original place as a figure in the background of certain scenes. The Flanderization of all of the characters is actually many fans' biggest complaint.
It was implied in the Yin/Yang saga episodes that Shawn's "zaniness" is a way of coping with increasingly stressful situations. Lassiter's change from a more or less humorless Inspector Lestrade to being a misanthropic creep (at least pre-Marlowe) is also explained by the stress following the dissolution of his marriage.
Gordon Ramsey's persona has steadily become exaggerated, especially when making the jump from British to American television. While he was always prone to impassioned speeches—and to peppering those speeches with the occasional swear word—it eventually devolved into flying off the handle at the slightest mistakes, and spewing profanity in all directions. Of course, sometimes it's edited to appear worse than it really is, and sometimes he plays it for laughs.
Rebelde Way: Marizza was always passionate and fiery about the things she cared for, but she also had a noble side to her that appreciated honesty and owned up her mistakes when she did wrong. Come season 2, and much of her rebelliousness comes off more as brattiness; forming protests for trivial, small things like room rearrangement, dismissing her caring mother yet instantly bonding with her real father once she meets him (despite him not grown up with her, therefore her newfound love for him is very contrived), and mistrusting Pablo EVEN after he did all in his hands to show the school he was on their side and wasn't going to support the cruel actions of his father of closing the school. And yet she believes all the lies all the other boys tell her, oddly enough.
In Red Dwarf, the Cat started out as a strange, vain man who didn't particularly like his shipmates and was perhaps a little dim. By series 7, he was entirely The Ditz.
Kochanski, in her first appearances, was intelligent and competent, but flirtatious, with a good sense of humour - someone who could plausibly date Lister. When she reappeared in Series 7, the dominant factor in her personality was that she was stereotypically female. Justified as the version of Kochanski from Series 7 is from another reality (and played by The Other Darrin) and implied to have had a different upbringing entirely, such as going to an English boarding school, rather than growing up in Scotland.
A minor one for Lister - he was a mediocre guitarist in the first season, but by season 6 his playing was so bad that he was only allowed to play in the vaccuum of space and was described by Kryten as a "ten-thumbed, tone-deaf, talentless noise-polluter."
In his early appearances in the first two series, Captain Holister is portrayed as a competent, if flawed, commanding officer.When he reappears in series 8, he's suddenly turned into the ultimate Pointy-Haired Boss who can hardly run a bath.
A blend of Flanderization and Anti-Character Development happened to poor Much in Robin Hood, as he went from the unappreciated servant of a lord who nevertheless demanded respect and stood up for himself, to the completely whipped slave of a bratty peasant girl. After two seasons of being the Butt-Monkey, Much finally lets loose with a passionate rant to Robin on how he's sick and tired of being treated like crap. The fans rejoiced! Surely Season Three would involve Much coming out of Robin's shadow and regaining some self-respect. Instead Much takes the pride that he's wrestled back from Robin and sacrifices it all to Kate, who treats him even worse than Robin ever did. He spends the entirety of Season Three running around after her, (even spoon-feeding her at one stage), and is then forced to watch as Robin and Kate hook up, despite both of them knowing about Much's feelings.
The worst victims were Mark (who went from being a troubled teen with a hidden good streak and some hints of under-education from dropping out, to a complete idiot who actually burned his hand repeatedly in one episode because he was bored) and Jackie (who started out as a bit neurotic and insecure but generally a competent single female to a complete nutcase who would erupt in to nervous, annoying laughter at the drop of a hat. By the final seasons, it was no small wonder that she somehow managed to hold down a job, keep her house and not have child services take her kid away).
Perhaps no character suffered this more than Leon. Originally Roseanne's uptight boss and later an equally upright partner in the diner, his homosexuality eventually became his defining trait as well as gaining several stereotypical traits he previously didn't have.
Rules of Engagement: After the first couple seasons Adam became incredibly stupid. The actor doesn't mind.
Morgan was introduced as a shallow but still capable girl with a few ditzy moments. In season 7 she is a complete ditz complete with a whole new way of speaking.
An in-universe example happens in the episode "When Teens Collide" where Libby and Sabrina accidentally swap personalities and each becomes an exaggerated version of the other. Sabrina becomes power hungry and tries to use her magic to take over the world while Libby becomes sickeningly nice and cheerful.
Saturday Night Live has had many recurring characters over the years who have suffered from this trope. Perhaps one of the most specific examples is Anthony Crispino, played by Bobby Moynihan. Anthony began his run as a guy who "updated" Seth Myers at the "Weekend Update" desk on the latest headlines he heard secondhand, always getting them wrong in some way ("This President Obama....apparently, he's a socialite"). Seth would correct him ("I think that's 'socialist,' Anthony"), and Anthony would let loose with a long high-pitched noise halfway between an "uuuuuhhhhhh" and an "aaaaaahhhhh," ending with a sputtering "I'm pretty sure it was 'socialite,' Seth." In his last (so far) appearance, the high-pitched cry supplanted the humor of his malapropisms (and his habit of turning his head from left to right to see if anyone was listening) to the point where the writers were parodying the cry itself, at one point replacing it with the audio of a soprano hitting a high note.
Saved by the Bell: Screech was originally a quirky genius, but his growing stupidity was epitomized when he became an assistant principal in Saved by the Bell: The New Class. With Screech, it's not that he's stupid (He was salutatorian of his class.) He simply has no social skills. But it did, indeed, get worse as the series went on. So it still counts.
Who remembers when J.D. was just a little emotionally needy due to him wanting a father figure to replace his own dysfunctional family? Fast forward to season five where J.D. is an appletini (light on the tini)-swilling "sensey" (that's "sensitive person") who can't hold on to his "man cards" (which would be taken away from him if he did something girly) for a full day. This is lampshaded by Zach Braff in the bloopers to Season 8.
"You haven't been here in a while, my character's really gay now."
Carla was initially a tough cookie Team Mom. As the seasons went on, the writers Flanderised her obsession with gossip and her domineering tendencies over Turk. She also went from giving advice to forcing her opinions on everyone else and admitting that taking the moral high ground "is like crack for me".
Elliot went from being a pretty normal, slightly quirky, girl with no interest in kids and a high degree of efficiency coupled with no personal skills to highly neurotic, obsessed with getting married and having kids, and the most compassionate doctor in the hospital that was only there because she wanted to help people. This case is at least justified by the fact that she was getting older and thus had a stronger desire to settle down in some sense.
Seinfeld's main cast Flanderizes greatly over the course of the show, as do many of the minor characters.
Kramer is perhaps the most noticeable, going from a quirky but ordinary fellow into an eccentric mastermind who regularly breaks the law, social expectations, and maybe even the rules of physics. Elaine goes from a forward-thinking woman to being short-tempered, neurotic, and vain. George goes from being a relatively unsuccessful but otherwise mature individual into a bastion of failure who explodes at the smallest lack of success. Of the three, only George's Flanderization is lampshaded or mentioned in-universe. Jerry is perhaps the only main character who stays unchanged, although his finicky tendencies toward cleanliness and girlfriend-perfectionism surface pretty regularly.
Newman is probably the most prominent example of Flanderization among the secondary characters—he is merely an annoying neighbor to Jerry in his first few appearances, but not long after becomes Jerry's arch-nemesis who seeks to undermine him at all costs.
Jerry's character traits did get spoofed, though. In one episode, he meets a woman who's just like him, which he considers an excellent relationship. Over time, though, he wants to break up because he thinks she's too much like him.
Jerry's Jerkass traits were flanderized during the last two seasons. Granted, he was snarky and shallow right from the beginning (except maybe in the Seinfeld Chronicles pilot). But, once Larry David left the series, his snarkiness in particular was taken Up to Eleven. In episodes like "The Bizarro Jerry" and "The Suzie", just about every line he says is a sarcastic quip.
In general, all the characters began as average people with average moral compasses, the sociopathy that they became famous for only appearing in the later seasons. An example is the second season episode where George and Elaine accidentally get a busboy fired after George explains to the manager that he left a menu too close to a candle and caused a small fire and Elaine jokes that she's never eating there again. Both are eaten up with guilt and George even goes to the guy's apartment to apologize, only to make things worse when he accidentally lets the busboy's cat get loose, causing him to feel even more guilty.
Chloe from Smallville went from someone who was okay with computers to being able to trace a bug's point of origin, discover anything about anyone, and she even had a shot at decoding a Kryptonian virus on her PC... when all the power on Earth had been shut off. Basically she filled in any plot holes where the writers couldn't think of a way to get Clark to the place he needed to be. Brainiac downloads its intellect into her, pretty much super-Flanderizing her computer skills; it turns out he was responsible for her intelligence going out of control and she was losing more and more of herself as time went on.
Mycroft in Sherlock, while notably thinner than his literary origins, still refuses to perform "legwork". However, in the Sherlock Special The Abominable Bride, he's presented so far in the other direction it's almost a parody. Granted that Victorian!Mycroft is (likely) just a figment of Sherlock's imagination as part of moving a puzzle, it may just be Sherlock getting a dig in at his brother
Ronon Dex from Stargate-verse, who went from a ruthless tactical soldier and runner in his introduction to Dumb Muscle by the end of the series. Slightly justified as he's very rarely given the chance to be tactical, since nearly everyone around him is a Science Hero and are able to come up with an easier tech solution to deal with the current problem.
Of course, there was that one episode where Ronon and Teal'c took care of a Wraith infiltration into SGC all by themselves.
The Applied Phlebotinum and alien races. Jeffries tubes? Mentioned a few times in the show as an alternate route when doors won't close; mentioned in all spinoffs as where everything is. Warp core breach? When first mentioned, it was so absurdly unlikely due to all the redundant safeguards that the characters couldn't understand how it even happened; but before long, the writers were using "warp core breach" as a go-to danger so often that it seemed a core would breach if you even looked at it funny. Even in the spinoffs themselves, some time between Picard's transformation to Locutus and Star Trek: First Contact, the Borg became Space Zombies!
A character-specific version afflicted Mirror Universe Intendant Kira in Star Trek: Deep Space Nine. According to Nana Visitor, her sexualised approaches to her mainstream universe counterpart were originally meant to be a narcissistic interest in the Screw Yourself possibilities, but the later mirror universe episodes turned her into a fanservicy Depraved Bisexual, somewhat to Visitor's displeasure.
Q started out as an omnipotent cosmic being sent to judge humanity's worthiness to continue to explore the universe and eventually transformed into Janeway's wacky neighbor on Star Trek: Voyager. Even worse was his appearance on Deep Space Nine where he was reduced to being a sniveling brat who begs a mere mortal (Picard's ex) to continue being his playmate. TNG's version of Q would never have sunken so low.
Several intelligent species started out fairly nuanced if vague, and with time were turned into Planet of Hats. The Klingon from the first series era are shown to be crafty and devious when the situation calls for it, instead of the simple-minded "ATTACK NOW!" mentality they degenerated into later. One side effect of this was that Klingons gaining a cloaking device before the Federation was explained away as being a Romulan contribution rather than something they developed themselves. The Ferengi directly attacked Enterprise in their first appearance, but during Deep Space Nine it was stated they never had any wars because war is less profitable than having peaceful trading partners. Even the Ferengi concept of heaven contains beneficial trading relationships galore! In Voyager, the Borg assimilating was taken to such extreme that they are unable to develop new innovations themselves! If a Borg cannot solve something with the options it has beforehand, it will keep repeating them mindlessly instead of trying to come up with a new solution.
Voyager badly exaggerated the crew's attitudes towards the past, with 20th century buff Tom Paris being the only one who wasn't completely mystified by anything that existed in the audience's present. Occasionally this even started interfering with what was going on elsewhere in the franchise at the same time, like Harry indicating that holodecks are the sole form of entertainment and he sees anything he can't interact with as being dull, when over on Deep Space Nine Jake was launching a career as a novelist.
Dr. Lu Delgado on Strong Medicine. She starts off with a chip on her shoulder about rich people and as a bit of a Straw Feminist. Both traits are fairly understandable as she grew up in a poor neighborhood where she frequently saw the end results of that poverty—teen pregnancies, drug use, domestic violence, etc. But as the series progresses and by the time it ends, both traits get completely out of control to the point where every episode can be expected to have at least one scene where she will spend five minutes screaming her head off about whatever social injustice was being addressed, and her attitude toward rich people now borders on reverse snobbery, while her attitude toward men borders on flat-out misandry. And no matter what the situation was, no matter how she handled it, Lu always comes out on top and is always portrayed as being in the right.
On The Suite Life of Zack and Cody, London Tipton started out as the shallow, somewhat snobby rich girl who had her airhead moments. Gradually, the airhead part became more and more prominent. On the show's spinoff Suite Life on Deck, she's a full-fledged ditz with occasional signs of Hidden Depths.
Dean unfortunately has a few of these now. Another one is how he "makes everyone family." In the first six seasons or so of the show, Bobby gets Promoted To Parent and Dean forms a family unit with Lisa and Ben while believing Sam to be dead. He also clearly views Cas in a familial role. From late Season 7 to early Season 9, however, Dean in short order refers to Cas, Charlie, Benny and Kevin all as "family" with utmost sincerity, causing fans to joke that Dean has decided that anytime he likes someone, they should be family.
The brother's relationship has also undergone this in later seasons. Dean's all about Sam now, to the point where he will literally choose Sam over the world, and Sam is nearly Driven to Suicide when he thinks he's let Dean down. While the more extreme bibro fans eat this up, others have found the brother's codependency to be getting less sweet and more disturbing as the show has progressed.
this has quite clearly happened is in how Dean treats Sam's love interests. In Season 1, Dean actively encouraged Sam to pursue a relationship with Sarah. Not just sleep with her- Dean tries to get Sam to take her out on dates, and offers to drive back through town a few weeks later so Sam can visit her. By Season 4, his issues with Ruby are more than warranted, but also come across at times as straight-up jealousy. By Season 8, he's so clearly jealous and resentful of Sam's former relationship with Amelia that it borders on Incest Subtext (even for fans that don't ship it), even though Sam left her before reuniting with Dean, Dean never actually meets her and he knows nothing about her. Sam doesn't seem bothered by Dean's sexcapades (which, as established above, are mainly unattached one night stands anyway), but now flips out at the idea of Dean getting a "new brother" or trusting anyone above him.
Castiel in season 4: Badass angel of the Lord with a mild curiosity about human behavior. Castiel from season 7 onward: Socially awkward, klutzy nerd. Seeing him in the later episodes, you'd be hard pressed to believe he was once a completely serious character.
The angels in general have their obedience flanderized by later seasons. In seasons 4-6, they were shown to be somewhat hesitant to accept that the apocalypse didn't need to happen -which, to be fair, was a plan several millenia in the making, endorsed by the archangels, and apparently created by God, whom disobeying is the single greatest crime an angel can commit. By season 9, the angels have become a bunch of sheep who will blindly follow anyone who looks like he could be in charge, regardless of intention, if it'll save them the trouble of thinking for themselves.
John Winchester got this posthumously. He was hardly portrayed as a "good" parent at any point, but each of the brothers acknowledge at different times that John did the best he could under crappy circumstances, John himself admits on several occasions that he was too hard on the brothers growing up and wasn't really a father to them, and he tries to redeem himself by going to Hell to save Dean's life. While Sam seemed to develop a better understanding of John after his walk on The Dark Side a few years later, Dean and other characters became increasingly disillusioned with John, until by Season 5 he was an abusiveJerk Assdeadbeat who left the brothers alone for weeks on end (as opposed to "days" in Season 2), was a brutal disciplinarian to Dean and seemed to barely interact with Sam other than barking orders or arguing with him. Even Bobby is shown in a flashback arguing with John about being too hard on the kids, and it's implied that this was the reason behind John and Bobby's future estrangement. They try to reverse this somewhat in Season 8, with both brothers again acknowledging that John did the best he could, but it's back in form with Season 9, when a flashback episode shows John parking teenaged Dean in a "boys' home" for two months after a minor infraction- and Dean being happier there. Jeffrey Dean Morgan, the actor who played John Winchester, has even joked that he'd like another appearance in the show just to "set the record straight."
Bobby got a bit of this as well before being Killed Off for Real in Season 7. In the earlier seasons, he was a gruff, no-nonsense hunter with a Dark and Troubled Past who helped the brothers out of jams on occasion and had a bit of a soft spot for them. He was later Promoted to Parent, and in seasons 5-7 nearly every time he's on screen focuses on either his close relationship to the brothers or his own emotional issues, including a never-before-mentioned debilitating alcohol habit and a viciously abusive father.
Bob from Teachers started off as a stern boss in the first series before turning into a more easy-going, if awkward character. This later was Flanderized into him being the Butt-Monkey, with his wife leaving him in the third series and reaching its peak in the fourth, with his new Thai bride (who refuses to have sex with him but does so with his replacement as head of English) and his wearing of an ill-fitting toupee.
Chelsea on That's So Raven went from an occasional (but still likable) ditz to an even worse one who irritates even her best friends.
Eric, Kelso, Donna and Fez. Eric turned from a relatively normal teenager into an absolute nerd; Kelso went from awkward and indecisive to plain stupid; Donna became so aggressive that she was a borderline Straw Feminist; and Fez, formerly a classic desperate virgin, turned into a pervert. Also, Red was a somewhat stern, but no-nonsense parent who still had a nice side (although he'd hard-pressed to admit it) in the first season, but as seasons went on, he became a constantly angry introvert that borderline terrorised and bullied Eric.
Eric was further flanderized the seasons preceding actor Topher Grace's departure from the show. As stated above, he is shown as obsessed with Star Wars despite showing no more interest in the movie than Kelso. Similar to the Scrubs example, he became a disco rollerskater with no knowledge of sports, though this varied depending on the episode.
Kitty started out as a fairly normal TV mom who occasionally drank, but by the end of show, she was an unstable, smothering alcoholic. This was somewhat justified as her increased drinking seemed to be a direct result of her children growing up and needing her less. The first time she drank more than usual (Red commented that she usually only had one drink and Kitty snapped that tonight, she was having two) was when Eric wanted to have a birthday party alone with his friends because he was too old to have the surprise party Kitty had thrown him every year. It makes sense that as her children grew up, became less dependent on her, and eventually moved out of the house (and the country, in Eric's case), Kitty's tendency to drink would become more prominent.
In the first two seasons of Three's Company, Chrissy was a rather intelligent character with only the occasional Dumb Blonde moment. By the time she left the show, she had evolved into the naive, rambling airhead that she's usually remembered as.
At the beginning of Tim & Eric Awesome Show, Great Job!, Dr. Steve Brule was basically a lovable idiot whose blank stares and lack of common sense simply left you wondering how he WAS a doctor. Over the course of five seasons of "Tim and Eric" and then two seasons (so far) of Check It Out! with Dr. Steve Brule, Dr. Steve became a rather mentally damaged human being, who can't pronounce simple words correctly and seems COMPLETELY out of touch with reality, becoming an unexpectedly sympathetic and tragic figure as he gains self-awareness of his failures at gaining friends and romantic partners and reveals his horribly dysfunctional and abusive family.
The presenters on Top Gear have self-Flanderized into Clarkson (aggressive loud boor who likes power and shiny things), Hammond (small hyperactive hamster who wants to go really really fast) and May (slow, cerebral pedant who can't be bothered with any of that).
Same thing happened to the cast of Top Gear (US). Tanner went from racing expert to The Cast Showoff who would take every opportunity to rub it in the other's faces, Rutledge went from his title card job of "The Expert" to the Butt-Monkey and Adam just boiled down to the guy who picked cars made for the elderly.
Jake's childish naivete and gullibility have developed into adolescent stupidity.
Alan's poverty is under fire from the joke writing staff a couple times each scene he's in. Plus, he's more of a geek and a freak than ever with a streak of bad luck.
Alan's Flanderization becomes increasingly apparent in the later seasons. Formerly just broke, unlucky and socially inept, he becomes a shameless freeloader with no pride or dignity, incredibly cheap, more clumsy and unlucky than ever, dimwitted, socially retarded, and increasingly jerkish.
Judith has become a full-out she-devil who has absolutely no compassion for her ex-husband she is pressing for money.
Charlie became more and more of a Jerk Ass every season, and now Alan has turned into a spineless whiny mooch who has no moral high ground and his Jerk Ass traits are starting to rival Charlie's.
Donna goes from a snarky, somewhat sardonic individual to one who is incredibly bossy and sometimes violently angry in later seasons.
Then there's Louise, who started the series as a naive, narcissistic, somewhat manipulative, not particularly intelligent girly-girl, with a touch of quirkiness about her. By the seventh season, she is incredibly manipulative, sometimes very spiteful and bitchy, very snobby, and incredibly self-centered - to the point where she names her newborn child "Louise Louise" (after spending an episode not wanting the child because of her fears that it would be "prettier" than her). She also goes from not minding Jonny at all (and not showing a hint of disgust when he kisses her in the episode 'Lard', and stating that she actually likes him "in a way"), to outright despising him for the most trivial of reasons (she even gets him shot by the police, after she gets a job at the Office for National Statistics and changes his profile to that of a serious criminal).
Jonny's "feminine side" being exaggerated in later seasons is another example.
Believe it or not, The Vampire Diaries finds a way to make this work and reference it In-Universe. When a person is turned, their traits are magnified. Said best by Caroline:
"So you're saying I'm an obsessive, control freak...on crack?"
Victorious was hit with this pretty badly. In Season Two!
Jade was one of the more sane people on the show despite her callous tendencies and had some decent depth. She quickly turned into psychotic and vengeful Manipulative Bastard and has stooped to lows such as stealing a pint of blood that Tori donated just to keep her from performing in the school play, as well as attempting to kill the first ever Hollywood Arts prom.
Cat started off as down to earth, not too smart but not too stupid either. Come season two, she became mentally retarded, unable to pay attention to anything. This continued into the Sam & CatSpin-Off.
If anything, with the spinoff it got unbearably worse. Though as awful as she became, she was not nearly as torturous as every appearance of BOOMER!
Robbie somewhat in Season 2 and the beginning of season 3 on the subjects of him being cheap/selfish, having incredibly bad luck(especially with girls) and being a near Sinjin-level loser. Luckily, they pulled back and he's back to his geeky but sweet personality from season 1, if not a little more characterized.
Beck seems to have become a bit of a jerk since he and Jade broke up.
In Weeds, Doug goes from the somewhat childish, well off accountant in the earlier seasons, to a incompetent man baby as the series progressed. This happens sharply after they relocate to Ren Mar, and by the sixth season its surprising he can change his own diapers. This may be due to the fact they try to give him some depth by highlighting how his life has fallen apart.
Karen's shrillness and addictions, and Jack's shrillness and idiocy on Will & Grace.
Also Grace became much more neurotic and self-obsessed, and Will became much more whiny and his Camp Gay tendencies along with Jack's increased.
In a glorious evidence of tropes are not bad, Wipeout. A show whose appeals are mostly in schadenfreude and Hurricane of Puns commentaries, the commentators will reduce every contestant (post-first elimination anyway) to a caricature based on whatever funny thing they said/behaved like earlier, however slight. This is done light-heartedly and taking it away will leave the hosts to essentially a constant, uninteresting set of remarks ("oh sensible guy #12 fell down the water how hilarious!!!").
Justin was represented as a smart, collected bookworm, who loved rules and never broke them. Lately, he has become an almost vicious, revengeful badassMad Scientist, who has used magic more than once. And that's becauseofAlex.
Justin's and Alex's innocent Sibling Rivalry turned into a spiteful, dark enmity that is characterized by revenge and loathing. The affection they expressed quite visibly in the first two seasons was reduced dramatically and by the the end of season three, they barely speak to each other like two normal people. In fact their lines towards one another mostly consist of insults and snarky phrases.
Jerry and Theresa, although frustrated with Alex's trouble making, were loving parents none the less. Now, Justin seems to be their only child they actually like.
Theresa has become increasingly narcissistic and self-obsessed, to almost Miss Piggy levels, so much that it has become almost the sum total of her character.
3rd Rock from the Sun At the start, Dick was a slightly vain yet competent leader who genuinely cared for Mary. By the end he was an insufferably egotistical asshole with a near sociopathic callousness towards his team's problems and took advantage of Mary whenever he thought he could get away with it. Sally went from an aggressive but cautious and clever security officer trapped in an attractive non-threatening female body to an insane mess of a character who switched between solving every problem with violence and a stereotypical shallow cheerleader unable to throw a punch. Tommy used to be the mature voice of reason, the oldest and smartest member of the team who ironically had to deal with being in an adolescent body. Cue him turning into a sex-crazed pervert with little if any respect or concern for the other teammates. Harry was always the oddball, but had elements of usefulness like being the group's link to their homeworld. Somehow he ended up absolutely irresistible to women and getting more action than the rest of the cast, despite his child-like personality. Mary was a smart, capable professor with a sarcastic streak and implied family issues. Her final characterization was one that was willing to sleep with anything that moved, was stupidly and insanely devoted to Dick, and had serious psychological problems coming from bad relationships with everyone in her family. The minor characters had this happen as well, particularly Don who went from a melodramatic cop to an absolute sleaze who hid from the slightest hint danger.
Chloe O'Brien on 24 underwent this during season 3. She changed from a quirky analyst in her first few appearances to a neurotic wreck (who also happened to be the only thing standing between CTU and complete system failure) by the end of the season. This characterization more or less continued through the next three seasons, and only reversed itself once Chloe assumed control of CTU New York in season 8.
In the early seasons of 30 Minute Meals, host Rachael Ray was quite calm, comparatively quiet, and did not use many acronyms in her speech. There were only a few hints to her underlying quirkiness. Over the run of the show, she transformed into a hyperactive, noisy, acronym-using parody of what she once was.
Many characters, but none more so than Jenna Maroney. Jenna started off as Liz's neurotic, somewhat shallow best friend. By season three, being an Attention Whore was basically her entire personality and she had as big an ego as Tracy. And from that point on, she only became more and more of a cartoonishly self-centered diva.
Writer John Lutz started out as a normal, albeit undesirable member of the writing crew, but as time progressed became more and more of a Butt-Monkey to the point that he now only appears on-screen to be humiliated or personally injured.
Kenneth's status as a humble Georgian boy from a small town was originally supposed to make him charmingly sheltered and innocent. As the show progresses, he becomes a steadily more grotesque and creepy character whose Southern background is exaggerated into a sort of Deliverance-style horror, while his weird habits and general cultural alienation from the rest of the cast grow so extreme it's occasionally implied he may not be quite fully human.
Peter Dickson, more famously known as the E4 Voice-over Guy, was a rather noticeable over the top TV announcer for British TV channel E4. However he soon became a Cult Hero and he has since got more and more over the top. So much so that if you hear anything with The E4 Voice-over Guy that isn't so ridiculously over the top and ruddy silly then you think it's not the real Peter Dickson. Compare this older promo with this new one.
Lampshaded in a British Government radio advert where he starts as his usual bombastic self. He then talks with his normal voice to advertise the new Bureau of Career Advice, he just sounds really odd.
Jessie is a particularly bad example, even among Kid Coms that tend to dumb down characters over time. Literally every character has been heavily beaten with the Flanderization stick over time, no exceptions.
Let's start with the title character herself, Jessie, who used to be a very competent young woman with a touch of social awkwardness and a dating horror story or two. By the end of the series' run she's almost literally incapable of doing anything except publicly humiliate herself (except when the plot rarely calls for otherwise) and her entire romantic life consists of dating anyone who happens to be an even bigger loser than herself. It's gotten so bad that these two characteristics are pretty much her sole defining ones (which has the unfortunate side effect of making episodes rather predictable too, again even for a KidCom).
Then there's the oldest kid Emma. She used to be a pretty normal teenaged girl, a little fashion obsessed and a little ditzy. Again, by the end of the show's run she's become an Idiot Savant in fashion yet about as dumb as Jessie when it comes to anything else.
Luke likewise went from a typical teenage boy to Too Dumb to Live and incapable of understanding the concept of hygene.
Zuri was a soft but affable example of a Sassy Black Woman who was arguably more characterized by her cuteness and naivety (first season episodes focused on her imaginary friends). By the show's end she's veered almost straight into Jerk Ass territory, with the show somehow expecting the audience to still find her sympathetic.
Bertram always had a tinge of Jerk Ass qualities but is now full-on this with Unsympathetic Loser.
Liv and Maddie: Joey was a typical sitcom teen loser nerd but his loser qualities became Flanderized to the point where he's no longer even considered smart. The Einstein Sue role in the show has since been picked up by his young brother Parker - which oddly enough subverts the Flanderization rule since this is a quality he's he spontaneously picked up.