“Grey's Anatomy” handed Dr. Isobel Stevens a fateful choice on its fifth-season finale Thursday night. Izzie had to decide if she should have risky brain surgery for the cancer that has plagued her. In another development on Thursday's two-hour season-ender, Dr. Meredith Grey (Ellen Pompeo) and her beau, Dr. Derek Shepherd, were wed. Well, sort of. Last week, they had given up their fancy ceremony, so that living-on-borrowed-time Izzie could marry her fiance, Dr. Alex Karev, instead. Since cast member T.R. Knight is widely believed to be leaving the series, in the episode's crowning twist, O'Malley was revealed to be the unrecognizably bloodied, injured John Doe who had pushed a woman out of the path of a bus and been struck by it himself.
