In a recent sit down chat to celebrate the 15th anniversary of 2008's Iron Man, the film's director Jon Favreau and Marvel boss Kevin Feige discussed their original plans for Robert Downey Jr. pre-MCU.
According to Favreau, who you might recognise as 'Happy' Hogan, Downey Jr. was originally put forward to play none other than the Fantastic Four's nemesis Doctor Doom.
Favreau said: "I remember you had all met with [Downey Jr.] already for like Dr. Doom or something on another project.
"I think he had come through on maybe Fantastic Four, so everybody sort of knew who he was."
Of course, Downey Jr. wouldn't be selected for this role, and while it's unclear how far through the casting process he got, the two were happy with the final decision to use him as the face of Marvel's Iron Man.
In fact, Downey Jr. 's presence on the project seems to have been what got the ball rolling towards the MCU in the first place.
Favreau said: "Once it was [Downey Jr.], that's when my life got a lot easier because he understood the voice of the character.
"And then one by one, people were just signing on board because now it became something interesting."
Feige added: "The tone that [Favreau] and Robert discovered on that movie, I would say became the template in a way for much of what the MCU became.
"I remember on later movies - we'll talk about them on the 15th anniversary of those - there were dark days.
"And I would say to Robert 'We wouldn't be in this mess if it wasn't for you.' Meaning, we wouldn't have a studio if it wasn't for him."