The Doc Brown of Back to the Future Part II goes through a lot of changes, but then the actor had to go back and find the character who had experienced none of that.
Trying to recapture a character you played before is probably a potentially difficult problem for a lot of actors when they go back to make sequels, the problem is only compounded when you’re dealing with a time travel movie, as you then find yourself playing what is essentially the same character, but one that is still slightly different in many important ways.