A Funny Joke-And what did your Father do?

A joke from http://www.amazingjokes.com/
And what did your Father do?
The teacher says, "Let's discuss what your fathers do for a living." Mary says, "My Dad is a lawyer. He puts bad guys in jail." Jack says, "My Dad is a doctor. He makes all sick people better." The teacher says, to Dirty Johnny, "John, what does your Dad do ?" Johnny says, "My Dad is dead." She says, "I'm sorry to hear that. But what did he do before he died?" Johnny says, "He turned blue and shit on the carpet."