Bruce Willis is joining the cast of "Alpha Dog," which New Line Cinema will release domestically. Willis will play the father of the main character in the film, which is inspired by real events and tells the story of Johnny Truelove (Emile Hirsch), a young man from Southern California's San Gabriel Valley whose ambition is to follow in his father's footsteps. When one of Johnny's plans goes awry, his father is forced to step in and save his son from a life behind bars. The film also stars Sharon Stone, Justin Timberlake and Dominique Swain. "Alpha Dog" is being produced by Sidney Kimmel Entertainment in association with A-Mark Entertainment. Chuck Pacheco and Sidney Kimmel are producing, with Marina Grasic executive producing. Butch Kaplan, Scott Nicolaides, Steve Markoff and Robert Geringer also are executive producing.