Campbell was a regular on the sitcom Herman's Head (as the desire-driven Animal) and has guest starred on Seinfeld, Strangers with Candy, and The Practice. In films, he was featured as sloppy naval cook Buckman in Down Periscope (with Kelsey Grammer and Rob Schneider) and had smaller roles in Home Alone, Groundhog Day, Breakfast of Champions (as Eliot Rosewater), Coyotoe Ugly, and Bewitched. Campbell also supplied the voice of Baby Bob, the talking infant, in a series of commercials and a short-lived sitcom. Other voice credits include Challenge of the Go-Bots, God the devil and BOb, Titan A. E., and Dr. Dolittle 2.