Terry Zwigoff's penetrating, thoughtful, and disturbing 1994 essay about the great underground comic artist Robert Crumb, who's best known for Fritz the Cat and Mr. Natural as well as his "Keep On Truckin'" drawings, though he's also a semiprofessional musician and connoisseur of early jazz and blues. Made over a six-year period, the film offers an intimate, multifaceted portrait by a longtime friend and fellow musician that's exceptional in many respects. For starters, it presents Crumb not as a comic-book artist but as an artist, plausibly described by critic Robert Hughes as "the Brueghel of the second half of the 20th century." Then it goes on to show how difficult it is to assess artists, exploring in considerable depth Crumb's dysfunctional family background, sexual obsessions, working methods, and political positions. By the end of two hours we're persuaded that if Crumb weren't drawing constantly and compulsively he would probably be as doomed as his brothers Charles and Max, both of whom are also comic-book artists. Never letting his participants or his audience off the hook, Zwigoff traces the ideologically and psychologically ambivalent stances Crumb takes toward his art through the perceptions of several friends, acquaintances, relatives, former lovers, and Crumb himself. We're not only shown a complex human being and the range of his art, but are also guided through a profound and unsettling consideration of what it means to be an American artist. Essential viewing. Music Box, Friday through Thursday, May 26 through June 1.