Robert Lyle Knepper 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 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 season 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.
Born in Fremont, Ohio, Knepper was interested in acting from an early age due to his mother's involvement at a community theater. He was raised in Maumee, Ohio, near Toledo, by his mother and father, who was a veterinarian. Knepper spent many years of his youth working in the community theater and high school productions. After graduating from Maumee High School in 1977, he attended Northwestern University to study drama. During this time, Knepper also obtained professional roles in plays in Chicago. Nearing the completion of his degree, Knepper quit Northwestern and went to New York City, where he continued to work in theater. Although Knepper never intended to work in film and television projects, he began his television and film career in 1986 with The Paper Chase and That's Life!.
He recently guest-starred in Criminal Minds in the Season 6 episode, Reflection of Desire as Rhett Walden, an insane serial killer who believes that his dead mother is actually alive.
On August 26, 2011, Knepper, along with three others, was honored by the Maumee Alumni Association during an awards dinner and at the opening Maumee High School varsity football game.