Jon Favreau is a triple threat in 'Iron Man 2,' the upcoming sequel to the successful comic book blockbuster, serving as director, producer, and actor. He tells ET's Thea Andrews about casting the award-winning Mickey Rourke in the film.

He said, "Once we thought of him, we started developing the costume and the design of the character around him."

It wasn't necessarily easy to nab the Golden Globe winner. Favreau said, "His career got very busy as he was doing all the award season stuff and it took some time to make everything work out, but he was enthusiastic from our first meeting."

In 'Iron Man 2,' Rourke stars opposite Robert Downey, Jr. Rourke plays the roles of Ivan Vanko and Whiplash, while Downey, Jr. reprises his roles of Tony Stark and Iron Man. Favreau thinks this is a compatible casting, saying "I think he's a very formidable adversary to Robert Downey, Jr."

Downey, Jr. is excited to work alongside the Oscar nominated actor. He said, "We knew he would bring something to a nemesis character that would make it more engaging and more dimensional." He continued, "I had seen him in 'The Wrestler' and I knew from the time I saw that, this was something special."

Watch the video to see Mickey Rourke fire things up on the set of 'Iron Man 2' and to hear what cast mates had to say about working with the star. To see ET's interview with co-star Scarlett Johansson, click here.