What's worse than a pile of a thousand dead babies...?
The live one in the middle eating its way out.
I know, it's a horrible joke, and there are plenty of others (appropriately called, Dead Baby Jokes.) You hear them, laugh and then hate yourself for doing so. This is the best way I can describe Heath Ledger's performance of The Joker in The Dark Knight. He is as scary and menacing as Hannibal Lecter, but you can't help but hate yourself for chuckling at him every now and then.
Ledger's performance is one of the the great examples of an actor becoming completely lost in a character. From the first moment he is on screen, the audience forgets everything they were thinking about Ledger and his unfortunate death. Only The Joker is on screen, and he is as original and frightening of a character as has ever been seen.
His origins are not explored in the film, something Nolan explains by saying that he wanted to depict the character as an "absolute." This works perfectly in the film, as the Joker is a pure agent of chaos that jumps in and out of the story. Yet, much to the credit of Ledger, he is completely believable. The way he walks, licks his lips and tells stories (stressing the plural) about how he got his "smiling" scars is completely within the realm of human possibility, which makes him that much more frightening. Without any explanation for his existence, the audience is scared to death that, in a world as grounded in reality as Nolan's Gotham City, this man could exist. As for his humorous aspect, he's as funny as Steve Buschemi being fed into a wood chipper. Each time I've seen the film, the entire audience can't help but laugh as an entire hospital is razed to the ground. We hate that we're choosing to laugh, and The Joker will play the same joke on our heroes.
As I have said earlier, The Joker is the catalyst for the emotional changes within the film's main characters. It isn't unusual for heroes to see themselves in their villains. Nolan, in fact, employed this technique wonderfully in his previous film, The Prestige. It is, however, unusual for an entire cast to be so affected in so many ways by one person. Just as his basic plans seem to be foiled, he forces them to make impossible moral choices, mocking, all the while laughing at, their personal struggle. Sick as it may be, he finds it funny that people can so easily be manipulated.
Earlier, I suggested that Ledger's Joker was much like Hannibal Lecter. He is not the film's main focus, but he is easily what will last in the mind of the audience. His evil is horrifying, but completely believable (which makes him that much more horrifying.) The Joker, though "absolute," is a complex character explores the nature of good and evil in a completely original manner.
All this being said, his case for an Oscar is a complicated one. While the academy is normally prone to liberal guilt, see: the bullshit that is a Best Picture award for Crash, they seem hesitant to be so for the deceased. At this point in the year Ledger's Joker is the best supporting role I've seen. Whether or not this is true when the final votes are cast, I hope the academy will evaluate his performance in the same manner that they do the rest.