LOS ANGELES (AP) — Robert Downey Jr. is officially back in the superhero business. Production started Wednesday on "Iron Man 2," the sequel to his 2008 blockbuster about the Marvel Comics character.

Downey reprises his role as a billionaire genius who fights bad guys in a high-tech metal suit that's loaded with gadgets. "Iron Man 2" reunites Downey with co-star Gwyneth Paltrow and also features Don Cheadle, who replaces Terrence Howard as the superhero's military ally.

Mickey Rourke is signed on to play a villain, and the cast also includes Scarlett Johansson and Samuel L. Jackson, who had a cameo at the end of the first "Iron Man."

Jon Favreau is back directing again for the sequel that hits theaters May 7, 2010.

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