Don't know know, Trav?

Nolan's filming a completely seperate & fake movie alongside TDKR about Talia and the League of Shadows. Robin Williams is also in talks to take a day off from his broadway show to meet with Nolan for coffee, so that our spies snap pictures and presume he's Hugo Strange. And whilst only cameoing as a Cop for the actual film, Joseph Gordon Levitt signed on specifically to show up in Pittsburgh in a Robin Costume for a day. Josh Pence isn't really in the movie either, he has a knack for signing onto films where you won't actually get to see his face and WB took advantage of this.
It's all part of Nolan's elaborate plan to throw fans off from the real story. He's simply brilliant