Danny Glover has joined the cast of the big-screen version of Dreamgirls as Marty Madison, the manager of Eddie Murphy's James "Thunder" Early.... Variety reports that Robert De Niro is set to star in What Just Happened?, Barry Levinson's upcoming film based on Art Linson's experiences as a Hollywood producer. Sean Penn, minus boat and shotgun, is among the actors who will appear as themselves in the pic.