Excerpt from The Killing Joke

This here is from Batman : The Killing Joke. Which was Heath Ledgers inspiration behind his version of the joker. Even the story was modified to fit in with Harvey Dent. In the comic, Joker was trying to make Commissioner Gordon go insane instead of Harvey Dent.

Joker (while running away from Batman in a house or mirrors)

But my point is. My point is I went crazy. When I saw what a black, awful joke the world was. I went crazy as coot! I admit it! Why can't you? I mean, you're not unintelligent! You must see the reality of the situation. Did you know how the last world war started? An argument over how many telegraph poles Germany owed to its War Debt creditors. Telegraph poles! HAHAHAHHA! So why can't you see the funny side? Why aren't you laughing?

Batman (smashes through a mirror and grabs the Joker)

Because I heard it before. And it wasn't funny the first time.