Robert Lyle Knepper (born July 8, 1959) is an American actor. He is best known for starring as Theodore "T-Bag" Bagwell in the Fox network's drama series Prison Break, for which he was nominated for a Satellite Award. He has also appeared in the films Hitman (2007) and Transporter 3 (2008), and joined the cast of Heroes for its fourth and final season as Samuel Sullivan. He joined the cast of Stargate Universe for its second season, which aired in the US in the 2010 fall season. Knepper reprised his role as Theodore "T-Bag" Bagwell in the first season of Breakout Kings.