Ironettes dance scene
I'm just guessing that the Stark Expo opening scene was shot largely in components, to be composited together in post.
-There may have been only limited shooting with Tony and the dancers at the same time, so they wouldn't need to coordinate both performances. We know there was some joint filming from this: http://www.comicbookmovie.com/iron_man/iron_man_2/meet-the-ironettes-renee-herlocker-a16634
Maybe it was that last shot of the dancers when they're all seen together with Tony in the circle.
-Audience crowds are frequently multiplied by compositing, an added in post, so the director doesn't need to coordinate the crowd and the actor's performance.
Was anyone there who knows?
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