Robert Downey Jr. reveals at Comic-Con he'll play Marvel film villain Doctor Doom

Robert Downey Jr. revealed in a surprise announcement at San Diego Comic-Con that he'll return to the Marvel Cinematic Universe — not in his iconic Iron Man role, but as villain Victor Von Doom, aka Doctor Doom, in the Avengers series.

Downey kicked off Marvel's movie successes in Iron Man and played the popular character in nine films, but on Saturday, he appeared on a panel wearing Doctor Doom's mask and a green cloak.

"New mask, same task," Downey said to frenzied cheers.

Joe and Anthony Russo, who will direct the movie featuring Downey, said his appearance in the film is "proof of the unimaginable possibilities in the Marvel multi-universe."

The reveal capped a jubilant return by Marvel to Comic-Con's Hall H.