"George once said a really useful thing when I began playing Palpatine (in Star Wars: Episode I The Phantom Menace), and I don't know if he remembers this. He said, "In a sense, your eyes are contact lenses." In other words, the Palpatine character was the most artificial-it was as if they had grafted his face and put in (his) eyes. Because the real Palpatine is the one who bursts forth at a calculated moment in Episode III just after persuading Anakin to kill Mace (Windu). That is when the true person comes out, letting the evil fully manifest itself. The Emperor that you see in the last film looks the way he does because he's very old and very evil-it is what he always looked like. He just had this carapace of looking like a fairly ordinary looking guy, a politician that smiled a bit, and so on."
"I don't think George had made up his mind when we started shooting whether to continually show Lord Sidious as he really is after his initial transformation or if Sidious would go back forth with his appearance. I (believe) when George finally saw Dave's wonderful makeup he decided that constantly changing Palpatine's appearance would be a step backward. So the moment in the film where I make the transformation is the way I appear until the end. It's an interesting sort of study in schizophrenia really-the nice guy you saw was revealed later in the monstrous mask as the self, the Sith self."
"You think about Dr Jekyll and Mr. Hyde-Jekyll was the good doctor who went out at night and transformed into a terrible decadent, Hyde, who was buried down inside. In Episode III, it's more like Hyde in the guise of Jekyll throughout the film. And although the face is hideous, he doesn't care-Hideous Sidious, they go together."