Robert Downey Jr. thinks 'Iron Man 2' will "flip expectations".

The 45-year-old actor, who plays the Tony Stark and his alter-ego Iron Man in the movie, admits some cinemagoers may be surprised by the storyline of the film.

He said: "I'd always thought that we know Tony is a little nuts, so why don't we play with the expectations about the kind of stuff he does?

"I want to surprise people. There are some characters you may have heard are against Tony - well, we try to flip those expectations."

The leading man also admits the success of the first movie meant there was less worry about what would work on screen with director Jon Favreau.

He said: "The best thing is that the first movie went well enough that there's not much second guessing my and Jon's instincts about what works, you know?

"For no good enough reason, the folks at Marvel decided we were a very apt team with our far-out ideas of how to put a different spin on a superhero movie."

'Iron Man 2' - which also stars Scarlett Johansson, Mickey Rourke and Samuel L. Jackson - is released globally in late April and early May.