• Story-wise, the latest installment is said to mirror the comic thanks to the addition of a geneticist named Aldrich Killian, played by Guy Pearce, who invents the so-called Extremis serum, a nanovirus that both Iron Man and terrorists battle for control over.
• Ben Kingsley is aboard to play a supervillain who at one point was rumored to be The Mandarin but Marvel has yet to confirm the character's identity.
• Giving credence to the Mandarin theory, however, the production is slated to head to China once filming is completed in North Carolina.
• When it comes to Tony Stark's leading lady, Gwyneth Paltrow's Pepper Potts is going to have some competition this time around: Franchise newcomer Rebecca Hall (The Town) has signed on for the part of a "sexy scientist" that was originally supposed to be played by Oscar nominee Jessica Chastain.
• Jon Favreau, who helmed the original Iron Man and its 2010 sequel, will not be back in the director's chair for this go-around, handing the reins over to The Kiss Kiss Bang Bang filmmaker. But he is returning as Tony Stark's bodyguard and de facto sidekick, Happy Hogan.
• Don Cheadle is also back as Col. James Rhodes, otherwise known as War Machine, while The Pacific's James Badge Dale joins the cast as Lt. Col. Eric Savin. He ends up stepping on a landmine only to be resurrected as a cyborg villain named Coldblood, who presents a clear and present danger to our cast-iron hero. Ashley Hamilton is supposedly in negotiations to play the government cyborg baddie Firepower.
Robert Downey Jr. Starts Filming Iron Man 3—Here's Everything You Need to Know! - E! Online