How about mixing up the books and glasses!? hee hee, I'm so evil!
What's really funny is people simply leaving their Carnival towels on the chair. How in the world do you idetintify one blue towel from the other? It's a sea of blue towels! I just move the towel onto another chair. If there is nothing to indicate life(drink glasses, suntan lotion etc) near that chair then it's mine.
I should call myself HappyEvilCruiser ! tisk tisk