Jon Favreau draws Robert Downey Jr. and Gwyneth Paltrow's genuine dialogue for Iron Man

Jon Favreau recognized Robert Downey Jr.'s extraordinary impact long before he became a Hollywood heavyweight and an Oscar winner. 

"Robert is always interesting," Favreau reveals to PEOPLE. 

"That is a superpower." This insight led him to cast Robert as the lead in the 2008 blockbuster Iron Man.

A key ingredient to the film's success was Downey's chemistry with his co-star Gwyneth Paltrow, who portrays Pepper Potts. 

Their breezy and authentic exchanges on screen mirrored their real-life conversations incorporated by Jon into the film.

The director recalls his role as a keen observer during rehearsals, diligently taking notes as the actors engaged in improvisations or discussed scenes.

One notable instance occurred when Paltrow corrected a script detail during rehearsal, enlightening the team on the accurate reference to Jackson Pollock's artistic period. 

Favreau recounts how he documented Gwyneth's correction, incorporating it into the film to enhance the dynamic banter between the characters.