Just before the final press conference, Tony Stark is reading the newspaper with a grainy, amateur photograph of Iron Man on the cover. The picture is part of a video, shot by onlookers hiding in a bush during initial filming, that appeared on the Internet in 2007.

To prepare, Robert Downey Jr. spent five days a week weight training and practiced martial arts to get into shape, which he said benefited him because “it’s hard not to have a personality meltdown […] after about several hours in that suit. I’m calling up every therapeutic moment I can think of to just get through the day.”

Robert Downey Jr. had an office next to Jon Favreau during pre-production, which allowed him greater involvement in the screenwriting process. He brought a deeper sense of humor to the film not present in previous drafts of the script. He explained, “what I usually hate about these [superhero] movies [is] when suddenly the guy that you were digging turns into Dudley Do-Right, and then you’re supposed to buy into all his ‘Let’s go do some good!’ That Eliot Ness-in-a-cape-type thing. What was really important to me was to not have him change so much that he’s unrecognizable. When someone used to be a schmuck and they’re not anymore, hopefully they still have a sense of humor.”

The scene where Pepper helps Tony replace his arc reactor was filmed using a prosthetic chest, joined to Robert Downey Jr.’s own chest and projecting out at an angle, while Robert was ‘in’ the back of the seat he was sitting on. A bright light was positioned shining on the area to hide any potential ‘edges’ of the fake chest-piece.

For the Iron Man trilogy, Jon Favreau thought of making the Iron Monger the main villain of the second film. Stane was going to be Stark’s friend and confidante in the first film, but then would become his enemy in the second installment. However, Favreau was worried how to handle The Mandarin, whom was to be the villain of the first film, so he decided to re-work the character into a behind-the-scenes presence and make Iron Monger the first villain.

When Robert Downey Jr. was carrying out motion-capture work on the film, he would sometimes wear the helmet, sleeves and chest of the Iron Man armor over the motion-capture suit to realistically portray Iron Man’s movements.

To create the shots of Iron Man against the F-22 Raptors, cameras were flown in the air to provide reference for the dynamics of wind and frost at that altitude.

The Industrial Light & Magic animators studied skydivers performing in a vertical wind tunnel to create Iron Man’s aerial movements. Iron Man was also animated to take off slowly and land quickly to make those movements more realistic.

The Iron Man Mark I armor weighed 90 pounds.

The script was not completely prepared when filming began, since the filmmakers were more focused on the story and the action, so the dialogue was mostly ad-libbed throughout filming; Jon Favreau acknowledged this made the film feel more natural. Some scenes were shot with two cameras to capture lines improvised on the spot; Robert Downey Jr. would ask for many takes of one scene since he wanted to try something new. Gwyneth Paltrow, on the other hand, had a difficult time trying to match Downey with a suitable line, as she never knew what he would say.