Martin Eugene Mull (born August 18, 1943) is an American actor who has appeared in many television and film roles. He is also a comedian, painter, and recording artist. As an actor, he first became known in his role on Mary Hartman, Mary Hartman and its spin-off Fernwood 2 Night. Among his other notable roles are Colonel Mustard in the 1985 film Clue, Leon Carp on Roseanne, Willard Kraft on Sabrina, the Teenage Witch, and Russell the pharmacist on the hit sitcom Two and a Half Men.