[imported_Wicked Steve]

The best cursing line ever in a cartoon is from Beavis and Butt-head. If you're not familiar with their style, their repertoire is limited to a lot of "dumbass"es, "fartknocker"s, etc, mixed in with comments and insults that may or may not be funny or make sense (and they laugh constantly). In one episode, though, Beavis says something stupid while they're watching a video, and instead of just saying "dumbass" or trying to make a remark about it, Butt-head just turns to him and deadpans,

"Beavis, you are one stupid son of a bitch."