I am reminded of a very telling moment in the film “The Saint” which features a tour de force performance by Val Kilmer adopting guise after guise in a totaly convincing manner.
At one point in the middle of te film he is confronted by the female lead who questions him “Who are you really?”
It is at this point I believe that Kilmer slips out of character and speaks as himself when he says “No one knows - least of all me.”
Kilmer is another ‘tough customer’, someone talented and spoiled because of it. On the 1995 set for Batmam Forever, Val was caught talking down to a crew member, He was being irrational and ballistic with the first asst. director, the cameraman, and the costume people. Joel Schumacher, his director, called Val on this behavior and said “It will not be tolerated any longer, not for one more second! Then we had two weeks where he would not speak to me, but it was bliss!”