AceShowbiz - Robert Downey Jr.'s association with Tony Stark in the Marvel Cinematic Universe (MCU) has become synonymous, but it could have been a very different story. As revealed in a retrospective celebrating the 15th anniversary of "Iron Man", director and co-star Jon Favreau disclosed that Downey had also auditioned for the role of Doctor Doom in "Fantastic Four" (2005).

"I remember you had all met with him already for like Doctor Doom or something on another project," Favreau recalled to Marvel boss Kevin Feige. Despite not landing the role of Doctor Doom, which eventually went to Julian McMahon, Downey's audition left an impression.

Favreau praised Downey as "the puzzle piece that made it all work" in "Iron Man". He described Downey's spark and readiness, which he witnessed during their initial meeting. Ultimately, Downey's casting as Tony Stark transformed the film and became the template for the tone and success of the MCU.

"That tone that you and Robert discovered on that movie, I would say became the template in a way for much of what the MCU became," Feige said to Favreau.

Interestingly, Downey ended up joining forces on-screen with "Fantastic Four" star Chris Evans, who portrayed Captain America after initially playing the Human Torch. Downey's portrayal of Iron Man spanned 10 films before his character's arc concluded in "Avengers: Endgame" in 2019. Despite the immense popularity of Downey as Tony Stark, Feige has shot down any hopes of his return, stating that the character's ultimate sacrifice will remain untouched.