Joke

So there's a little girl playing hopscotch at the front of her house while her mother hangs up the washing and her father mows the lawn. She says "Step on a crack and you break your mother's back,". The father laughs, until his daughter steps on a crack resulting in her mother's back breaking. The little girl's father looks in terror, she then says "step on a line and you break your father's spine,". The father closes his eyes waiting for his spine to break, but nothing happens. When he opens his eyes again he sees that he is ok, and nothing has happened to him. Suddenly he hears someone yell out "OW MY SPINE,". The father runs around the corner to see the mailman laying on the floor.