A man goes to the cinema to watch a film in the middle of the day. The only other person in the cinema is an old guy with a dog sitting in the front row. As the film goes on, the man can't help but notice that every time the hero is on screen, the dog wags its tail, but every time the bad guy appears the dog growls and bares its teeth.
When the film is over, the man goes over to the old bloke and says, “excuse me, but I couldn't help but notice your dog's reaction to the film. That was amazing!”
“I know!” says the old bloke. “He hated the book.”
Good one!