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) KATHERINE HEIGL, T.R. KNIGHT, ELLEN POMPEO, JACK AXELROD