Through six years as a singer of loony tunes that found inspiration in the mundane ("Dancing in the Nude," "Margie the Midget," "Noses Run in My Family") and earned him a diminutive but devoted following, Martin Mull maintained a mighty sense of self. If no one showed up at his gigs, it was their loss, not his. Out of a combination of defensiveness and egomania, he created a stage persona that exuded a smug arrogance totally out of proportion to the degree of success he had achieved—a character superficially similar to, but significantly smarter than, the one Steve Martin is currently overexposing. So when he was offered a part in Mary Hartman, Mary Hartman, a show that exalted the banal, he certainly wasn't about to let his total lack of acting experience stand in the way.

In the role of wife-beating PR man Garth Gimble, Mull developed...