When Turk is confronting Todd about the surgery, at first he is actually talking to J.D. (his back is facing the camera; notice the blue scrubs and no surgeon's head cover). After Todd speaks and the shot turns back to Turk, he is now talking to Todd (green scrubs and head cover).
(At 10.04) Turk is talking to Todd about his views against plastic surgery on a 16 year old girl, for a brief moment Todd is in fact J.D. A switch over then shows that it is Todd again.