SAN DIEGO - Filming for Iron Man 2 finished just last week but thousands of fans got their first sneak peek at the star-studded new cast members this weekend at the Comic-Con convention.

Ten months before Iron Man 2 hits movie theaters in May 2010, fans saw Robert Downey Jr.'s industrialist-turned-playboy superhero Tony Stark working alone and considering another request to join forces with Nick Fury, played by Samuel L. Jackson.

In the brief footage, Mickey Rourke (villain Ivan Vanko/Whiplash) shows off his electrical suit with dual whiplash action, Don Cheadle employs a quick quip to address the change of actors for Col. James Rhodey Rhodes, and a red-haired Scarlett Johansson brings Natasha Romanoff (Black Widow) to life.

Iron Man turned Downey Jr. into an unexpected action movie hero in 2008 and made an impressive $585 million at the worldwide box office, making it one of the most successful Marvel comics film franchises.

Director Jon Favreau told reporters at Comic-Con that the team behind the sequel wanted to add characters -- although not too many -- and retain the same tone and dynamic of the first movie.

Downey Jr. added: Tony (Stark) goes on a much more perilous journey this time. You can't tell a story better than the way it really happened, so we started to look back at the comics. We didn't take ourselves seriously, but we took the story very seriously.

Favreau said Johansson turned up for their first meeting having already dyed her blonde hair red for the part. The actress said she also learned mixed martial arts for the role and did as many of her own stunts as possible.

We had an incredible stunt team. It was really just putting in the time training with the stunt team. If I see a movie, I like to see an actor doing their own stunts because you see their face and recognize their body movement. You want to believe it's them, Johansson said.

Cheadle was brought in to replace actor Terrence Howard in the sequel, after differences between the studio and the actor who played Rhodes in the first movie.

Fans got a look at how the change is dealt with. In a quick exchange during a Senate hearing in Washington, Rhodes surprises the courtroom and Stark says: I didn't expect to see you here, to which Rhodes replies, I'm here. Deal with it. Let's move on.

Favreau said that one of the goals of Iron Man 2 is to move the story forward toward the movie The Avengers that is planned for 2012. He said he hoped the Marvel Studios movies would continue to cross-pollinate their superhero characters.

Asked by a fan whether he would be directing The Avengers, Favreau was non-committal.

I still have another year on this one to go and to get ready to make 'Thor' with Kenneth Branagh directing, replied Favreau, who added that the prep work on Thor is looking fantastic.

(Producer) Kevin (Feige) and I haven't talked about that. 'Avengers' doesn't shoot until after 'Iron Man 2', he said.

(Editing by Jill Serjeant)