In Dusk's Dawn Donut doesn't notice anything suspicious about the antagonist after he claims that he's "obviously cured."
Coach Z on Homestar Runner. It seems that he only keeps his "more than two praeblams" (other than his butt fixation) for one episode. The whole cast plays dodgeball with the proverbial Idiot Ball.
The titular character IS an Idiot Ball, which is really almost the point of any short with him in it.
Really, everybody's held the idiot ball at some point or another. Even the more saner members of the cast (I.E. Strong Bad, Bubs, Marzipan) can go from Only Sane Man to complete looney in a matter of seconds. Even Strong Sad, probably the only consistently sane man, has his moments of utter craziness.