1. Queer old gentlemen from the 1950s who sit in your backseat for a living. They will certainly die if they are separated from the backseat. If you work for The Car Service and a backseatsman appears, you can never pick up anyone else again (unless he is asleep or has Downs Syndrome). They are also lacking severely in yo-yo skills.
2. See also: The Lonely Island.
1. "You work for The Car Service! There'll always be another fare!" exclaimed the backseatsman.