Tony Stark Did Improv — Robert Downey Jr. as Iron Man

While shooting the film, some 'Iron Man' scenes were shot using two cameras to capture improv lines because much of the dialogue for the movie wasn't yet written.

While the action scenes and plot were carefully scripted, much of the dialogue of the movie was not. Robert Downey Jr. would ask for several takes to try new things.

Reports claim that this style of acting frustrated Gwyneth Paltrow who had a rough time keeping up with Downey in improv situations.