I generally have a hard time casting known actors for book characters as I read, so I end up with a mental picture that is completely imaginary. Then the book is turned into a movie and I'm left wondering, What were they thinking to cast him/her?

I've heard O'Toole mentioned a couple of times now, among others. I still don't have any idea who could be a better Dumbledore, I just know that Gambon's interprestation doesn't work for me.