Neither of my children understands what a joke is. They mangle them, they make up decidedly unfunny stories, and they yell a lot about the failure of the other child's joke. Out of all this, though, my son inadvertently came up with something funny That is, after I thought about it quite a while, I realized he did a good job of standing a genre on its head. Here it is: "A man walked into a bar and said . . . ouch!"