History TookALevelInDumbass / LiveActionTV

* KC from ''Series/{{Degrassi}}'', he's introduced as a member of the school's gifted program, two seasons later he thinks there's four trimesters during pregnancy.

* Cosmo from Series/TheFairlyOddParents qualifies. While he was always dumb, it just got worse and worse and so much worse as the show continued, coupled with his voice going up a few octaves to be nigh unbearable.
** On that note, Mr. Turner also suffered from this, with him going down the exact same path (minus the vocal pitch change). Mrs. Turner seems to have mostly been spared, however.

* A lot of characters in ''Series/GameOfThrones'' lost their planning skills as the series [[OvertookTheManga caught up to the novels]] and the show writers no longer had examples of good strategy from the book series to copy, but none had a more drastic decline than Tyrion Lannister. He went from being one of the most cunning and manipulative characters in the series to being the precipitator of some of its biggest idiocies. In particular, in early seasons, he was probably the character who least trusted his malicious sister [[GodSaveUsFromTheQueen Queen Cersei]], but several episodes in later seasons have him inexplicably trying to appeal to a sense of duty, reason, and empathy that he should be very aware she doesn't have. "The Long Night" also has him hiding the civilian refugees in the crypts, when they're facing an enemy that can raise the dead as zombies. Yeah, even his own actor, Creator/PeterDinklage, lampshaded that.

* A lot of characters in ''Series/GameOfThrones'' lost their planning skills as the series [[OvertookTheManga caught up to the novels]] and the show writers no longer had examples of good strategy from the book series to copy, but none had a more drastic decline than Tyrion Lannister. He went from being one of the most cunning and manipulative characters in the series to being the precipitator of some of its biggest idiocies. In particular, in early seasons, he was probably the character who least trusted his malicious sister [[GodSaveUsFromTheQueen Queen Cersei]], but several episodes in later seasons have him inexplicably trying to appeal to a sense of duty, reason, and empathy that he should be very aware she doesn't have. "The Long Night" also has him hiding the civilian refugees in the crypts, when they're facing an enemy that can raise the dead as zombies. Yeah, even his own actor, Creator/PeterDinklage, lampshaded.

** After gaining the ability to remote orb people in Season 7, she never considers [[DramaPreservingHandicap orbing out innocents]].
** Combined with TookALevelInJerkass in the beginning of Centennial Charmed, with her strategy to invisibly sneak up behind Cole and blow him up from the inside to try and kill him. First she calls Leo to '''practice this on him''', blowing up and risking the existence of her already-kinda-dead-and-decidedly-good brother-in-law/spiritual guide for no justifiable reason and without a second thought. Despite the dead guy reconstituting and telling her that it's not gonna work, she thinks this proves that her plan is utterly brilliant for killing a past-nigh-invincible conglomerate of Wasteland powers who she's already seen try and fail to kill himself with the sisters' strongest potion. Note that this is on the eve of Cole's birthday, at his lowest and most lonesome point, where he's resorting to telling himself Happy Birthday because no one else will. When she goes for it and thinks she did it only to get chucked out the window by a reconstituting Cole and have to orb into the bay to survive, it's hard to feel sorry for her.

* A lot of characters in ''Series/GameOfThrones'' lost their planning skills as the series [[OvertookTheManga caught up to the books]], but none had a more drastic decline than Tyrion. He went from being one of the most cunning and manipulative characters in the series to being the precipitator of some of its biggest idiocies. In particular, in early seasons, he was probably the character who least trusted [[GodSaveUsFromTheQueen Cersei Lannister]], but several episodes in later seasons have him inexplicably trying to appeal to a sense of duty, reason, and empathy that he should be very aware she doesn't have.