Pepper Potts

To prepare for her role as Pepper Potts, Gwyneth Paltrow read many of the Iron Man comic books, lent to her by her husband Chris Martin.

As Tony Stark's true-blue, brainy assistant, Pepper Potts practically runs his life — and manages to save it when necessary. Director Jon Favreau says he cast Paltrow with hopes she could redefine the character.
He said:"We played her like somebody who could go toe-to-toe with him, a little more of a Moonlighting dynamic as opposed to someone living in his shadow.”

Iron Man

A big fan of the Iron Man comic book series in taking on the lead role, Robert Downey Jr says he would make 15 sequels about the character if need be.

And the actor went all the way when it came to perfecting his superhero character Tony Stark.

Downey Jr set up his own office next to director Jon Favreau's in order to discuss his role at any given moment.
Stan Lee, the creator of Iron Man, had originally based Tony Stark on Howard Hughes, who in his opinion was one of the most colourful men of our time: an inventor, adventurer, a multimillionaire, ladies' man and finally a nutcase. Downey Jr described his portray as a near-impossible challenge of making a wealthy, establishmentarian, weapons-manufacturing, hard-drinking, womanising idiot into a character who is likable hero.

He spent five days a week weight-training and practised martial arts to get into shape for the role.

Brought up to date — with a bang

In order to bring the film up-to-date, director Jon Favreau made some changes from comic book to screen. The biggest and most controversial was the change of location from New York City to California. He said he felt too many superhero films had been set there.

Another change was a major part of Tony Stark's history. In the comics, Stark participated (and became Iron Man) in the Vietnam War — a battleground which Favreau later changed to Afghanistan as he said he did not want the film to be a period piece but instead give it a realistic, contemporary look.
As for villains, it was a tough choice for Favreau, who said it was difficult to find a proper opponent for Iron Man to face, because he wanted the film to remain realistic and not to go over into fantasy.

Favreau decided Stark would have a foe who would serve as a parallel, armoured opponent. The lesser-known Iron Monger, Obadiah Stane, was chosen as Iron Man's adversary.