The truth is...I am Iron Man.

The sequel to last summer's blockbuster, which began shooting three weeks ago and opens May 7, 2010, takes place six months after Stark revealed his identity as Iron Man, says director Jon Favreau. And the development is playing out with unexpected results. "How many superheroes are open about their true identities?" he asks. "We wanted to play with that idea. But it obviously has consequences — in his relationships, on the team. There are a lot of areas we can explore."

He hopes to have all other Iron Man 2 details locked down — even though he's sending dispatches via Twitter from the set. "It's never easy with summer movies, but we're trying to keep as much a surprise as possible," he says.

That means no new dirt on replacing Terrence Howard with Don Cheadle, or how the crime-fighting team S.H.I.E.L.D. will ultimately come together. Or how he'll work in new characters. Among those signed on for this go-round are Mickey Rourke as Whiplash, Scarlett Johansson as Black Widow and Sam Rockwell as Justin Hammer.

Favreau says that tackling the franchise a second time is easier because he knows the landscape. Something else would help, too: "I really enjoyed when we were a dark horse and no one knew much about us. ... I hope we can find that place again."