The FOX network will begin the new season of the series on January 8, 2006. The role that Astin will play has not yet been determined.
Jean Smart (Garden State), Connie Britton (Friday Night Lights), and Brady Corbet (Thirteen) have also joined the cast.
Keifer Sutherland is the star of the show about the events that happen in a 24 hour time frame to each character.
In the fourth season, agent Jack Bauer (Sutherland) will be trying to stop a terrorist from creating a nuclear bomb.