To mark the 15th anniversary of the first Iron Man film, which launched phase one of the MCU in 2008, Favreau sat down with Marvel Studios president Kevin Feige to discuss how Downey came to embody the role of Iron Man, aka Tony Stark.
“It wasn’t really until we cast Robert that we knew what the take was, and once we cast Robert, every decision became a lot easier,” he explained.
“I think that’s probably one of the greatest decisions in the history of Hollywood,” Feige said of Downey’s casting.
During the conversation, shared to Marvel’s official YouTube channel, Favreau recalled how Downey had originally auditioned for the role of Doctor Doom in Tim Story’s 2005 film Fantastic Four. The part eventually went to Australian actor Julian McMahon, with the project receiving mixed reviews.
“I think he had come through on like maybe Fantastic Four, so everybody sort of knew who he was,” Favreau recalled. He said he ended up bringing Downey in after seeing “that spark in him”.
“Once it was him, that’s when my life got a lot easier because he undersood the voice of the character,” he said. “And then one by one, people were just signing on board because now it became something interesting.”
“From that first screentest... he knew that this was his shot and it was gonna work,” Feige agreed.
Iron Man, which also starred Gwyneth Paltrow, Favreau, Jeff Bridges and Paul Bettany (in a voice role), went on to take more than US$585m (£473.8m) at the global box office.
Downey has since reprised his Iron Man role in two sequels, along with four Avengers films, Captain America: Civil War, and opposite Tom Holland in Spider-Man: Homecoming.
Feige said during his conversation with Favreau that Marvel “wouldn’t even have a studio” if it weren’t for Downey, joking that he once blamed him for “the mess we’re in”.