I came up with a joke yesterday:
We all know the story of the little boy who cried wolf: four times he ran up the hill crying 'wolf', when there was no wolf. All the villagers came out to scare the wolf away and when they saw there was no wolf, they shouted at him for tricking them and wasting their time, and he'd run down the hill laughing. On the fifth time there WAS a wolf so when the little boy ran up the hill crying 'wolf', he was ignored and the wolf raced into the village and ate everyone, apart from a three year old girl who the little boy raped.