[marchron]

[ QUOTE ]
Knock knock

Who's there?

Interupting pirate

Interupting pira-?

ARGGGGH!

[/ QUOTE ]
There's a whole host of them: Interrupting Cow, Interrupting Sheep, Interrupting Retard, et cetera.

Personally, I like to do a bunch in a row, then Interrupting Mime. Unfortunately, that's more of a visual joke.