The Hitchhiker is a crazy looking guy wearing a bone necklace that Bart picks up while driving, he insists they should stop for ice-cream. He briefly alludes to having been at a psychiatric hospital before having left the place. He mentions he doubts he was actually rehabilitated, and suspected the true reason for his being "released" was because the staff "really needed the extra bed."
Behind the Laughter
Hitchhiker is a character from the 1974 horror film The Texas Chainsaw Massacre. He has a cameo in the episode "Bart on the Road". His name is Nubbins Sawyer in The Texas Chainsaw Massacre 2 (1986). In some televised airings of the episode, his character and scene were cut.