Hitchhiker

A recurring stranger on the roadside, thumb out, always looking for a ride from whoever happens to be driving. He seems harmless enough at first glance — just a guy needing a lift — but his appearances have an uncanny habit of coinciding with things about to go badly wrong for whoever stops.

He's a running gag elevated by pure vocal commitment: Maurice LaMarche plays him utterly straight, folksy and untroubled, which makes the dread funnier every time he turns up. The joke never explains itself, and Futurama trusts you to notice the pattern and dread his next cameo.