Kellvin Chavez over at Latino Review recently sat down with a high up WB executive, and managed to get a seriously major spoiler out of him. From the Latino Review article, the exec had this to say about the Joker’s introduction into the movie;
The Dark Knight begins with the Joker robbing a huge bank (we’ve seen photos of this everywhere). The bank is where the mob and all the gangs in Gotham keep all of their money. The Joker takes this money and holds it “ransom”. The Joker then says to the mob and the gangs of Gotham, “If you help me take down Batman, you’ll get your money back. If not, I’m going to burn it all.” This is how the Joker assembles his army to take down Batman.
If that isn’t just one of the best ways to bring the Joker in to the movie, I don’t know what is. Check out my blog for more hypothesizing, if you care to hear what I have to say.