Sebastian Stan is a Romanian-American actor, known for his role as James Buchanan \"Bucky\" Barnes/Winter Soldier in the films Captain America: The First Avenger and Captain America: The Winter Soldier. He is set to reprise his role in the upcoming film Captain America: Civil War. He also appeared in the 2010 film Black Swan. On television, Stan portrayed Carter Baizen on Gossip Girl, Prince Jack Benjamin on Kings, The Mad Hatter/Jefferson on Once Upon a Time, and T.J.\" Hammond on the miniseries Political Animals. His role on Political Animals earned him a nomination for the Critics' Choice Television Award for Best Supporting Actor in a Movie/Miniseries.