The characters of SpongeBob SquarePants underwent massive Flanderization after the first movie, with the show's tone and style of humor switching from innocently eccentric, gentle and witty to loud, mean-spirited, and deranged, with an increased emphasis on slapstick and gross-out humor.
- SpongeBob originally started out as a playful, naïve, eccentric, and happy-go-lucky Manchild who was optimistic, energetic and childlike to a fault. He would make most decisions on a whim and was mostly oblivious to how annoying and at times disruptive his unorthodox shenanigans were to his nextdoor neighbour Squidward and the Bikini Bottom public at large. He always wanted to make friends with and help out everyone in Bikini Bottom — regardless of whether they liked it or not — with varying results. To some Bikini Bottom citizens, he came across as a caring and generous Nice Guy with a heart of gold, and to others an over-the-top, clownish nuisance. Despite his actions often having unintended negative consequences, SpongeBob always had good intentions and was very eager to please. He was also, on occasion, able to demonstrate a somewhat mature attitude when the situation called for it.
- His Flanderization, starting in Season 4, turned him into a gratuitously obnoxious, moronic, deranged toddler as opposed to the zany, enthusiastic Cloudcuckoolander he was in the first three seasons. He became extremely hyperactive and over-emotional, with a higher-pitched voice, a shriller laugh, and a tendency to burst into tears far more often, and for longer (there is even an episode about this). His treatment of Squidward became stalker-level creepy, his antics crazier and more dangerous and his mindset considerably more ignorant and childish to the point where any remaining trace of his adulthood vanished entirely and so he needs to have basic concepts explained to him. Even his facial expressions became much more exaggerated to make him come across as mentally unstable; many modern production images (such as DVD covers) depict him pulling enormous open-mouthed smiles with dilated eyes and large rosy cheeks.
- The reason he can't drive was changed as well. When it's first revealed that he failed the test 38 times, it's apparently because he gets nervous behind the wheel and panics. In later episodes, he's a Giftedly Bad driver who puts everyone in Bikini Bottom in danger behind the wheel to the point where he's a Sponge of Mass Destruction. It should say something that in the first episode he takes the test in he has no problem passing the Theory Test, but in a later episode he states that he was never able to get even a single question of the Theory Test right.
- Furthermore, the number of driving tests he's failed was bumped up from 38 times in the first season to over a million in the fourth (although this was retconned to 57 times later in the same season).
- And then there are episodes like "A Pal for Gary" and "Choir Boys", where he's portrayed as actually cruel to Gary (due to his obliviousness) and Squidward (whom he attacked on purpose) respectively.
- Season 13 pushed SpongeBob and Squidward's dynamic to the worst it's been. Episodes like "Plane to Sea" and "Yellow Pavement" revolve entirely around SpongeBob being Lethally Stupid and unaware of the clear torment he's putting Squidward through; such as laughing at him after a Plane Awful Flight he forced him onto in the first place, or snapping a bandaged Squidward's neck brace backwards because he wants to try driving. "Friendiversary" shows SpongeBob not only being aware of his torment, but actively seeing it as a good thing and being nostalgic over it ("Remember the first time I startled you into this trash can?").
- SpongeBob's attitude toward his job has changed too. At first, SpongeBob took great pride as the Krusty Krab's fry cook. He worked for pay like everyone else, like in the "Krusty Krab Training Video", where he asked Mr. Krabs for a raise. Despite admiring Mr. Krabs, SpongeBob isn't afraid to stand up to his boss when he gets tired of his schemes, like when SpongeBob got tired of buying things for Mrs. Puff and fought back against Krabs when he captured the Jellyfish to steal their jelly. Also, like everyone else, he had ambition and wanted to become a manager; this was part of the movie's plot. Though there were times SpongeBob liked his job too much (he broke down crying when he got fired the first time), it wasn't as bad as in later seasons.
- Nowadays, SpongeBob is a complete slave to the Krusty Krab and Mr. Krabs to the point of obsession. In the "Bummer Vacation" episode, he goes completely insane after being told to have a few days off from work. The yellow sponge also has no problems doing extra jobs on top of the ones he already has and goes along with any scheme Mr. Krabs gives him without a second thought. He doesn't even have a problem doing any of it for free; later seasons imply that he's working at the Krusty Krab for free or for less. Season 7 would show that he's okay with being paid with play money rather than actual currency. SpongeBob's ambition is gone too, and he's completely content being a fry cook forever. In later episodes, SpongeBob would cover Squidward's and Mr. Krabs's jobs, and he'd be back in his previous post without fuss.
- His Flanderization, starting in Season 4, turned him into a gratuitously obnoxious, moronic, deranged toddler as opposed to the zany, enthusiastic Cloudcuckoolander he was in the first three seasons. He became extremely hyperactive and over-emotional, with a higher-pitched voice, a shriller laugh, and a tendency to burst into tears far more often, and for longer (there is even an episode about this). His treatment of Squidward became stalker-level creepy, his antics crazier and more dangerous and his mindset considerably more ignorant and childish to the point where any remaining trace of his adulthood vanished entirely and so he needs to have basic concepts explained to him. Even his facial expressions became much more exaggerated to make him come across as mentally unstable; many modern production images (such as DVD covers) depict him pulling enormous open-mouthed smiles with dilated eyes and large rosy cheeks.
- Patrick Star underwent two Flanderizations:
- He started out as an eccentric and fun-loving oddball who was slightly slow on the uptake but mostly intelligent (he even helped SpongeBob almost pass his boating test for the first time ever through radio; he immediately realized that Sandy's treedome was dangerous due to its lack of water; he was also able to pick up on Squidward's animosity towards him and SpongeBob, while SpongeBob was completely oblivious to it).
- His first Flanderization, which started around the end of Season 1, made him a lot more dim-witted and immature, sometimes stating bizarre non-sequiturs like "Is mayonnaise an instrument?". The animators would later accentuate his decrease in intelligence by giving him thicker, goofier eyebrows. During Seasons 2-4, his intelligence varies wildly. For example, in "Life of Crime", he forgets he's eaten a chocolate bar only a few seconds after eating it, while in "Driven to Tears", he demonstrates the ability to pass a driving test after only one try. He also makes an unusually intellectual statement once in a while, such as "The inner machinations of my mind are an enigma".
- His second Flanderization, starting in Season 4, turned him into one of the dumbest cartoon characters, his actions even becoming dangerous at times. He has also taken multiple levels of jerkassery. In earlier seasons, Patrick was a nice, funny and lovable dimwit who had his jerky moments, but it was hinted that he was just too dumb to realize the wrongness of his actions. However, his jerkiness got much worse and became much more frequent, up to Fat Bastard territory, going by the way he treats SpongeBob and Squidward on several occasions. Here are some examples:
- In "The Splinter", he makes SpongeBob's infection from getting a splinter worse by putting a pile of garbage onto it, assuming that it would make it "better". He also doesn’t seem to focus on SpongeBob's splinter well, despite the latter's pleas to have his splinter be removed.
- In "Big Sister Sam", he defends Sam's obnoxious behavior towards SpongeBob and Squidward and blames them for it.
- In "The Card", he goes as far as admitting that his stupidity is deliberate after walking through a whole bunch of dangerous places with a Mermaid Man trading card that he had bought for SpongeBob.
- In seasons 10-13, Patrick becomes an insufferable Fat Idiot whose jokes mainly revolve around his random bursts of anger, constantly eating things that aren't food (including diapers and other peoples' mail), and being Lethally Stupid to others. A good example is "Wallhalla", where his entire role consists of him barging into SpongeBob's house, eating urchin poop (which he mistakes for raisins) out of his fridge, stealing a package from SpongeBob's mother and flushing it down the toilet, and refusing to share his fresh Krabby Patty with a starving old man.
- Mr. Krabs went from being a typical greedy yet usually well-intentioned boss to being borderline Faux Affably Evil with an over-exaggerated Money Fetish who would go through several kinds of hell just to retrieve a single penny. One episode portrayed him as more obsessed with money as an object rather than for its value. While his greed was always prominent, he had some feasible redeeming aspects and morals to balance it out, his fatherly role with SpongeBob and Pearl for example. In later episodes, aside from some Jerkass qualities, his money-lust seems to be his sole defining trait, though this depends on the writer. In the first two seasons in particular he routinely was shown to have an emotional attachment to SpongeBob that has largely disappeared in later episode. It's also worthwhile noting that in earlier seasons, Krabs usually did receive his comeuppance every now and then with his (sometimes morally questionable) schemes. In later seasons, this is the total opposite — Krabs is practically one of the biggest examples of Karma Houdini, considering that he somehow gets away scot-free with anything he does in those seasons (ranging from theft to poisoning his customers to even driving people to suicide), sometimes leaving someone to take the blame/pay the price. There are even times near the end of some episodes when it looks like Krabs is about to receive his comeuppance (or in rare cases, actually does), but something happens at the end that puts the situation in Krabs' favor, if not lets him escape punishment entirely. On the other hand, he's been punished for his crimes in episodes such as "Patty Caper" and "The Cent of Money", and SpongeBob even calls him out for it on one occasion.
- Squidward's Butt-Monkey role was transformed from mere Laser-Guided Karma to a mix of outright Comedic Sociopathy and Kafka Komedy, with nearly every entity in Bikini Bottom genuinely out to make him miserable. This could be considered Character Development since it made his Jerkass (admittedly with a Heart of Gold) demeanor far more justified. Squidward's hatred of SpongeBob has also been Flanderized, though. For example, in "Christmas Who?", he gives away everything he owns so that SpongeBob won't cry. Episodes like "Gary's Got Legs" and "Broken Alarm" have Squidward outright gleeful at the idea of SpongeBob's death, excitedly coming up with increasingly horrifying ways for it to have happened in the former. He also flies off the handle too easily and screams nearly every time he's on screen. Seriously, you'd be hard-pressed to find any post-movie episode where Squidward goes for more than 40 seconds without shouting his head off at SpongeBob or anything else that annoys him in the slightest.
- Sandy started out as a Texas-loving tomboy whose primary passions were karate and daredevil behavior, though despite her rough exterior she clearly had more common sense than most of the cast. She had moments of more noticeable intelligence, most notably being a space traveler in "Sandy's Rocket," though moments like this were rare in pre-movie episodes. Starting around Season 4, she became a science geek while keeping her Only Sane Man tendencies and her love of karate and Texas culture, and a season or two later she gained a self-awareness of her many talents and evolved into a rowdy Ted Baxter. By this point they've also almost completely phased out her Texas Cowgirl tendencies for her scientist role, despite that her inventor traits were almost mute over the first few seasons.
- While Sandy's strength was very prominent early on, post-movie episodes tend to put very little focus on her strength and concentrate more on her intelligence.
- Plankton:
- While it starts as early as season 3, Plankton's Ineffectual Sympathetic Villain role is turned up to the point where he is arguably more likeable than his nemesis. His more general plans of causing destruction have become less apparent as his desire for the Krabby Patty formula has evolved into an obsession. His sentient computer 'wife', Karen's Deadpan Snarker mannerisms have also been upped to eleven.
- Season 13 would have Plankton undergo severe Motive Decay to the point where he can be either Always Chaotic Evil or just whine about his life depending on what's needed. He also Took a Level in Dumbass, such as trying to blow up the city with a stick of dynamite wrapped in toilet paper. "Captain Pipsqueak" even tries to say that his plans for "world domination" by stealing the Krabby Patty secret formula don't make sense, when that was never even why he wanted it to begin with. In "Lockdown for Love", he is completely unable to be faithful to Karen because he's too busy thinking about the formula.
- Originally, Mrs. Puff was just a No-Respect Guy who didn't want to have to deal with SpongeBob's bad driving. She was frustrated with his poor performance in her class, but genuinely wanted him to succeed and was generally nice to him outside of the classroom environment. Then she tried to murder SpongeBob in one episode after what she felt was the last straw (which apparently only lasted until the end). Since then, while she never goes as far as trying to kill him again, she still (if inconsistently) pretty clearly loathes him in or out of class. In season 12's "Kwarantined Krab", she tells SpongeBob that "outside of school, we don't know each other" and asks if someone can describe SpongeBob's suffering to her with a smile on her face.
- Her insanity and tendency to get arrested also became far more prominent after the Season 3 episode "Doing Time". Moreover, while in the pre-movie episodes her arrests were all due to legitimate destruction and danger caused by her and/or her student SpongeBob, in later years, they were for increasingly petty reasons.
