T.R. Knight (George O'Malley)
Plenty of characters have left Grey's Anatomy over the years. On the show itself, there are two ways you can go. You can have a tragic death like Derek Shepherd, or in the case of the most recent departure, you can find a way to see yourself out. Regardless of how a doctor leaves on screen, though, the story is always vastly different behind the scenes. In the same vein as the show, though, there are two options: to leave or to get fired. Many of the stars over the years have had pretty amicable exits. And then there are the other cases where some serious sh*t goes down and a bridge gets burned.