I've interviewed Robert Downey Jr. enough times now to know that the way it works is you give him a little question and you sit back and let that brain of his spin. The reason I can't imagine anyone else playing the Tony Stark we've seen in the Marvel movies so far is because that character is so closely tied to the qualities I've seen in the real Downey off-screen. In some weird way, the "Iron Man" films will eventually serve as a highly stylized form of autobiography, telling the story of Downey's enormous promise, his rocky years of self-destruction, and his eventual metamorphosis into the blockbuster-friendly charm machine that he's become.
We had twenty minutes with him. There were four or five of us around the table. When he strolled in, he had with him "The Box," his omnipresent collection of various vitamins and health supplements, and he looked healthy and happy. We jumped right in, asking him if he had any hesitations or worries about playing the character for the fourth time. "This is… the grab bag wish list of things we've always wanted to do and haven't had the chance," he said. He had his own expectations for the sequel, and they were hefty, to say the least. "[This] was supposed to answer all the questions for the audience, cure all my uncomfortable moments in the past playing this character, and get in every idea that fell by the wayside in the last three movies. Then we shot the movie and I feel like there’s still a number of other things we have to do."