Character Derailment in Family Guy.
- Stewie Griffin, previously a humorously sociopathic Enfant Terrible with matricidal tendencies, has become Brian's effeminate sidekick (the Doylist explanation was that the writers felt that they'd run the evil baby joke into the ground), though his violent tendencies do still occasionally show up.
- Brian Griffin experienced a couple distinct derailments. In the show's initial run, he was a snarky intellectual portrayed as vastly more intelligent than his owner Peter, sensitive and lovelorn, very earnest and sentimental, with an occasional tendency to fall into pretentiousness. When Family Guy returned from its cancellation, he was often the Only Sane Man and served as an on-screen preacher of the writing team's political views, much to the annoyance of many viewers. Perhaps as a corrective to this, he then evolved into a genuinely loathsome figure, an actual idiot who never actually read or accomplished anything. He's now The Chew Toy, and just about every character on the show looks down on him.
- Lois, while at first as the down-to-earth one of the family, albeit with a somewhat healthy sexual appetite, has become an insane nymphomaniac and Abusive Parent. This can actually be somewhat justified, as being married to and living with a man like Peter for years could easily drive the most sane, sensible person crazy. One episode even implies this by showing a tumor in her brain after she mentions bottling up all the stress that Peter causes her.
- Meg has evolved from merely a unpopular high-school girl trying to fit in to an abused psycho of epic proportions.
- Peter Griffin himself, while always a bumbling idiot but with slightly good intentions (like Homer Simpson, only fatter, brasher, and more into pop culture from the 1970s and 1980s), has become a Jerkass Psychopathic Manchild (making Homer Simpson look like the clueless, yet caring Bumbling Dad he was in the early days of The Simpsons).
- Around Season 11, Chris Took a Level in Jerkass just like his parents.
- Originally, Glenn Quagmire's obsession with women and sex didn't go farther than having a 50s swinger-type vibe, and was for the most part a happy-go-lucky Casanova Wannabe. He quickly became more successful in his pursuit of women, and eventually turned into an out-and-out rapist with a few offhand references to some of his conquests being underage girls. He went through a second derailment in later episodes, with his intense (and randomly produced) hatred for Brian and Self-Deprecation based neuroses becoming the focus of a lot of his humor. He eventually became far more bitter and cynical even in scenes without Brian, as opposed to the more carefree, fun-loving person he used to be.
- Quagmire definitely derailed in his ridiculous vendetta against Brian, despite the similarity of both characters; with Quagmire listing ridiculous, and hypocritical reasons— including, of all things, Brian's secret desire for Lois, despite Quagmire being guilty of the same thing; while Brian's desire is out of genuine love and romantic interest for Lois, against Peter's man-child ways, and Quagmire is simply a shameless pervert wanting what he can't have, including preying on Lois in a public restroom.
- Quagmire's inexplicable hatred for Brian, rather, seems to be a "Dennis Miller" like post-9/11 hypocrisy, of Quagmire being an airline pilot, and Brian being an arch-liberal; meanwhile Seth Mac Farlane voices both characters, and he narrowly avoided being a victim of 9/11 when he drunkenly missed his flight, which turned out to be one the planes that struck the Twin Towers. Likewise Macfarlane denied the event having any effect on him, while was basically a real-life version of Brian's liberal self; however this suppressed conflict seems the most likely explanation for the derailment.
- Joe became overly macho to compensate for his handicap as opposed to his original character which was more like a good cop who happened to be crippled. Later on in the series, his characterization swung back the other way HARD, with Joe becoming a sad, almost pathetic man who is a butt of every paraplegic joke whose wife resents him
- Mort, originally just a Sickly Neurotic Geek, was reduced to a caricature of nearly every Jewish stereotype you could imagine (despite not appearing much in the later episodes).
- Cleveland became much louder and dumber in his spin-off The Cleveland Show. If anything, he just became Peter, only black and slightly smarter.
- There's also something to be said for the derailment of Cleveland Jr. for the run of The Cleveland Show how he used to be a hyperactive child to a fat and slow teenager (though considering that Cleveland, Jr. disappeared after he kicked around a golf ball like a soccer ball in "Fore Father", who knows what could have happened to him between "Fore Father" and his appearance on The Cleveland Show's pilot episode?). The Cleveland Show episode "A Rodent Like This" reveals that the fat, weird, slow Cleveland Jr. is an impostor who killed the original and took his place and nobody noticed because they were too stupid, though that may have been a simulation. Like most of the Griffin family, he also Took a Level in Jerkass during that show's final two and a half seasons.
