Here's a Wiki cataloguing, with cited examples, all the eye-rolling idiot plots from sitcomdom.
Gilligan CutLink (Thanks, Gnat!)
The Gilligan Cut is a classic staple of comedy. A character protests vehemently, "What, you expect me to wear a grass skirt, stand up on top of Empire State Building and belt out the chorus of 'New York, New York'? Well, I'm not gonna... I'm just not gonna..." And then you cut, and see the character doing just that. The Gilligan Cut. Comedy ain't pretty.