The Joker made his way to the edge of his cell, smiling his trademarked painted on smile.  An hour before, he had received word that his cell security had been disabled, and was waiting for the perfect opportunity to show Gotham that he had escaped.  The joker tapped on the door of his cell getting the attention of the security guard.<br/><br/>"Mr. Warden Man, my psychological specialist has advised me that over the course of my life, I have come to associate humour with violence.  Therefore, by learning to laugh without hurting someone, I can facilitate my rehabilitation.  I would like you to help me by listening to a joke."<br/><br/>The Joker did not even wait for a response, and instead launched straight into the joke.  "Knock.  Knock."