Nicole Richie's fledgling acting career is officially at death's door. As reported in the current issue of TV Guide magazine (on sale now), the Simple Life diva recently filmed an episode of HBO's Six Feet Under to air Sept. 12. She'll play a celebrity who attends Claire's first art show and ends up purchasing one of her paintings. Sounds like she'll be playing herself, right? "They never say it's Nicole Richie," says her rep. "They never really call her by name." In related news, Paris Hilton has signed on to star as a sorority president in National Lampoon's Pledge This!