Beavis and Butthead used to demonstrate logical fallacies:
Circular causation
A chicken and egg situation. Not always the result of faulty logic, of course – life is often like that, as Butthead demonstrates here….
Beavis : How come Tom Petty’s on TV?
Butthead: Coz he’s famous, dumbass.
Beavis : Yeah, but how come he’s famous?
Butthead: Coz he’s on TV, buttmunch!
Beavis : Yeah, but how come he’s on TV?and so on….
(via Fark)