Martin Eugene Mull (born August 18, 1943) is an American actor, comedian and musician who has appeared in many television and film roles. He is also a 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, Vlad Masters / Vlad Plasmius on Danny Phantom, and Gene Parmesan on Arrested Development. He had a recurring role on Two and a Half Men as Russell, the drug-using, humorous pharmacist.