When Jack played the Joker, it was obviously Jack (same with Jim Carrey's Riddler, Danny Devito's Penguine, etc.). He did a great job, but you knew it was an actor playing a role. I had no idea who this "Heath" guy was going into the movie... not too up on tabloid info and am bad with names. Cece told me who he was after the movie. I have seen him in a few other movies (some I have watched multiple times), and I'd have NEVER guessed that he was the Joker. Very well acted. No accent, very disturbed & evil, and he even used a little of Jack's manner... great tribute to the great Jack Nicholson. The role was his, and he made the character believable.