Excuse the rant, but there have been several incarnations of the infamous Joker from the Batman comic books. From what I understand, the Heath Ledger Joker is the closest version of one of the most evil men ever to grace the pages of a comic book.
Forget the Jack Nicholson Joker, he shot a few guys but was not even remotely as twisted as the true Joker. And of course, the Joker in the 60s TV show was, well, a joke. Let me explain a few things about the nature of The Joker.
First, his makeup is ironic. He's laughing on the outside, but is truly insane and disturbed on the inside. Some people confuse insane with stupid. Please, don't. This man's IQ is up there with Batman's, the reason that he is, in fact, the match to Batman in every way. Just as Batman's psyche is twisted to do good, the Joker's is the same but opposite. He's his perfect match.
Now, let's look at a typical Joker crime, with some back story. In "The Killing Joke", probably the very best example of The Joker at work, he is a struggling chemical engineer who wants to be a stand-up comedian. He doesn't make it big, and ends up turning to crime, albeit assisting real criminals to commit a robbery, at the chemical plant where he used to work. During the planning of the robbery he finds out that his pregnant wife has died in an accident (see, this is not child's play).
The chemical plant robbery is foiled by Batman, and the man falls into a vat of chemicals (this is where Burton's Joker took inspiration from) and comes out with his bleached white face and crooked red smile.
Now, scarred inside and out, he commits a crime that is beyond what you'd see in even a movie like Saw. This, from Wikipedia, explains it all:
The Joker shoots Barbara Gordon (then known as Batgirl and in later comics as Oracle), paralyzing her. He then kidnaps Commissioner Gordon and taunts him with enlarged photographs of his wounded daughter being undressed, in an attempt to prove that any emotionally and morally stable man can become insane after having "one really bad day." The Joker ridicules him as an example of "the average man", a naïve weakling doomed to insanity.
Nice, huh? He murders one of the Robins, Jason Todd, in another novel. Commissioner Gordon's second wife also dies at the Joker's hands. And so it goes on.
So next time you think The Joker is a somewhat witty, funny-little guy, think again. He's as twisted and evil as any villain out there. And then some.
Oh, and The Joker is also so wickedly clever and sly that he is the only villain ever to have made Batman crack a smile, with this joke:
See, there were these two guys in a lunatic asylum... and one night... one night they decide they don’t like living in an asylum any more. They decide they’re going to escape! So like they get up on to the roof, and there, just across the narrow gap, they see the rooftops of the town, stretching away in moon light... stretching away to freedom.
Now the first guy he jumps right across with no problem. But his friend, his friend daren’t make the leap. Y’see he’s afraid of falling… So then the first guy has an idea. He says “Hey! I have my flash light with me. I will shine it across the gap between the buildings. You can walk across the beam and join me.” But the second guy just shakes his head. He says... he says “What do you think I am, crazy? You would turn it off when I was half way across."
