Well After Batman defeats the Joker(Who had shot Barb and kidnap Gordan in this very Comic, The Joker tells Batman a joke, after it is told they both laugh in the rain, and the comic ends there.)
There were two guys in a Lunatic Asylum and one night they decide they dont't want to live in an Asyum any more. They decide they are going to escape. They get up on the roof and there, just across this narrow gap, they see the rooftops of the town, stretching away to freedom.
Now the first guy, he jumps right across with no problem. But his freind, he didnt dare make the leap, he was afraid of falling.
So the first guy has a idea. He says Hey I have my flashlight with me. I LL shine it arcoss the gap between the buildings, and you can walk across the beam and joing me.
But the second guy just shakes his head. He says What do you think I am?? Crazy??? You turn it off when I was halfway across.
Joker
The Killing Joke.
Here is a short bio... there is a longer one but i don't remember where it is:
http://www.dccomics.com/secret_files/dc_character.html?sc_dc_itemCode=raven