". 
Why would Palpatine propagate his deformation by continuing to generate Force lightning? Some argue that he purposely disfigured himself to use as evidence against the Jedi in the Senate, and that given his personality, he wouldn't really mind the changes. How can one make such a presumption though? He's pure evil, we really don't know much else about him character wise. That's also part of what makes him so great, he's little more than evil personified... the Dark Side of the Force incarnate. Its far more likely that he looked like that before, the Dark Side corrupting his features over time. That would explain why his face looks perfectly symmetrical as a side effect of Dark Side abuse, rather than truely ""warped"" all in one shot. Remember, Lucas didn't create Palpatine in ROTJ thinking, ""He's human, and he looks so hideous because Mace Windu played by Samuel L. Jackson in Revenge of the Sith demanded a larger role and wanted to claim responsibility for something important."" When approached with a question asking him why the Emperor looks the way he does sometime after the release of ROTJ, Lucas answered that it was a side-effect of utilizing the Dark Side for so long over one's lifetime. He specifically likened it to cancer. They were originally going to make the change gradual over the course of the prequal trilogy, as exemplified by AOTC. As you can see, all of the makeup that made him look older in AOTC was not present in ROTS. Reason? Samuel L. Jackson. He had to whine and complain about having an impact and not getting killed by Clone Troopers like all of the other Jedi. George got him to shut up by having a not-so-noble death, and having it look like he beat Palpatine in a duel (specific quotes from Nick Gillard in the Making Of Revenge of the Sith book indicate that Palpatine acted the whole thing out, PERIOD. He even stressed it to the point where he suggested Ian add, ""SUCKER!"" to the his dialogue) Yeah right, all of the smart fans know better. Alright so Mace was duped, but Samuel was obviously pacified. Di Mace still make an impact? In a way, he did. He revealed the galaxy the true face of Lord Sidious"