Zack's bum has detached itself again. And before it absconded this time it almost killed Zack's kitten, Mittens, by a ruthless, lethal, sudden gas emission, any bum's particular talent. With no desire to explain things to the local bum-catcher for the fourth time in as many months, Zack pursues his errant bum, even though it is the middle of the night. He follows his bum all the way down to the local football stadium and gets the shock of his life: