"GREY'S ANATOMY - ""Let the Angels Commit"" -- Cristina scrubs in on the rare 'humpty dumpty' procedure, much to the envy of her fellow doctors, Alex questions his future medical specialty, George and Addison work with a pregnant woman with an unusual dilemma, and Derek receives a surprise visit from his sister, on ""Grey's Anatomy,"" THURSDAY, OCTOBER 26 (9:00-10:01 p.m., ET) on the ABC Television Network. (ABC/RICHARD CARTWRIGHT)SARA RAMIREZ, T.R. KNIGHT"