Abruptly departed: Isaiah Washington, center, T.R. Knight and Katherine Heigl Played: Hot-tempered Dr. Preston Burke, mild-mannered Dr. George O'Malley and big-hearted Dr. Izzie Stevens Lasted: Three seasons (2005-2007), five seasons (2005-2009), six seasons (2005-2010), respectively Why they left: The doctors were dropping almost as quickly as the patients in the first few seasons of the ABC show. Washington was ousted after an altercation with costar Patrick Dempsey, during which he allegedly used a homophobic slur to describe Knight. Knight decided to leave the show after weak storylines and a lackluster fifth season, and Heigl left to focus on her film career. How it went down on air: Burke got cold feet and ran off before his wedding to Dr. Cristina Yang, George was the nearly unidentifiable bus accident victim who heroically saved a woman before becoming severely disfigured. Izzie was fired after Seattle Grace's merger with another hospital and ultimately decided to leave Seattle to get away from her husband, Alex, believing he was the cause of her dismissal.