Joker tells his own form of joke. He tells batman about a man. He got married right out of college where he had majored in chemistry. His wife convinced him to forget chemistry and follow his dream of doing comedy. He didnt make money as a comedian, so they were poor but happy. When he discovered that his wife was pregnant he agreed to help a crime syndicate develop a new drug. They were busted when shopping for chemicals at a the chem. plant, and fearing he would be in prison when his daughter was born, he tried to escape through the chemical laden outflow of the plant. He awoke handcuffed to a hospital bed. He was told by the policemen in his room that he had been fingered as the leader of the chemical heist by his co-conspirators. Then he was told that his wife had been murdered execution style, presumably for his failure in the heist. And what is the punch line to this cosmic joke? His exposure to the caustic chemicals had eaten away his face. The doctors were able to repair his face, but the surgery left him with a permanent grin. Now, even in his deepest grief, he couldnt help but smile. The Joker says that is when he realized that life was a great cosmic joke, that someone up there was looking down on all our agony and despair and laughing. He also saw how delicate sanity is, and how one bad day can break a man. He says he will show the world they are walking a razors edge of madness, and perhaps then they will see how pointless and ridiculous it all is. They can see, as he does, the comedy in tragedy, the laughter in mans despair. Perhaps they can all be, as he is, in on the gag.