"We all thought it was really surprising that anybody thought there was a ghost on our show," Grey's Anatomy creator Shonda Rhimes told Entertainment Weekly after last night's season finale. (For much of the season, the character of Dr. Izzie Stevens saw and spoke with her dead boyfriend Denny, later revealed to be a hallucination caused by a brain tumor.) "We're a medical show. We thought it was surprising that anybody would look at it and go, 'Gee, that's a ghost.' So that was surprising to us."