In a recent interview with U.K. magazine Empire, Iron Man and Iron Man 2 director Jon Favreau said that his lead actor, Robert Downey, Jr. (RDJ), contributed far more than just his acting ability:
"Robert is a real partner in the process. He's been very involved in the [Iron Man 2] screenplay. When he went away to do Sherlock Holmes, he was still part of our creative process. Even in the first film, where he was originally a hired gun playing the role, he really stepped up to rewrite scenes - he's a great writer, too. So we really are sharing the responsibilities."
For his part, RDJ said that he had an intuition about how Tony Stark should be portrayed in the first film:
"I have fortified my belief that if I have a creative instinct about something, usually it's not because I've had too much coffee or because I'm bored - it's because I sense there's something there. And it's always mind-blowing when you follow a hunch and realise it's exactly what the movie wanted."
RDJ went on to say that they were not content to simply let the momentum of the first
Iron Man carry them through the sequel:
"We are grinding our minds and hearts in the ground on this movie. Could we have just skated through a sequel and would it probably have made the same box-office numbers? Yes, sure."