What could be his next character?

Now that Borat, Brüno, Aladeen and Ali G are all out, what could he do next?

I hope that, if he does create another character and a film with it, that it follows the mockumentary style, as it seems to work better than his scripted films. I'm sure he could pull it off again, with more make up, prosthetics, etc. And maybe going to another country as opposed to the US.

What do you guys think he should/could do next?