The Russo brothers, who are directing the highly anticipated Avengers: Doomsday, are recalling the first time they heard Robert Downey Jr.‘s Doctor Doom voice.

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While chatting with People at Comic-Con 2026 over the weekend, Anthony and Joe Russo said they already knew Downey Jr. was perfect for the villain role after early conversations with him. But once they heard the voice the Oscar winner had crafted for the character from the Fantastic Four comics, that’s when their decision was solidified.

“That was something that Robert surprised us with one day,” Anthony recalled. “You know, we were talking about all the details of the character — the voice, of course, is a key part of it, especially in the mask.”

“So one day I think it was in the trailer, we were just sort of talking about some ideas and he broke out into the voice. And we knew at that moment, that was it,” the filmmaker continued.

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Joe added that he got “chills” when he initially heard the Doctor Doom voice. It also reminded him of another iconic Downey Jr. scene from 2019’s Avengers: Endgame.

“I mean, it was one of those moments. It’d probably be one of the more memorable moments — that and the ‘I Am Iron Man’ [scene] when he snapped his fingers,” Joe says of the fan-favorite sequence. “Robert tends to present a lot of those super memorable moments.”

The upcoming film’s stacked cast includes many Marvel superheroes from the legacy Avengers and X-Men to the Thunderbolts and The Fantastic Four. They’re all expected to team up to face off against Doctor Doom.

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Avengers: Doomsday arrives in theaters Dec. 18.