Robert Downey Jr. was initially in talks to play a different Marvel character.
He gained global recognition as Tony Stark/Iron Man in the Marvel Cinematic Universe.
Director Jon Favreau revealed that Downey Jr. was interested in playing another character.
Downey Jr. was considered for the role of Doctor Doom in the Fantastic Four film.
Julian McMahon ultimately played the role of Victor Von Doom in the 2005 film.
Favreau saw Downey Jr. as the perfect fit for Iron Man, calling him the puzzle piece.
Downey Jr. understood the voice of the character and made the casting process easier.