Dr. Phil Perlmutter is the doctor House impersonates in the Season 6 episode Known Unknowns. He is an unseen character. In order to hide the fact he's not registered at a medical conference, House gives the name of one of the other doctors who have registered but haven't shown up. Later, when House realizes Wilson is going to give a speech in favor of doctor-assisted suicide, he drugs Wilson and takes his place to give the same speech, still impersonating Perlmutter.