Robert Downey Jr. Had A Specific Pepper Potts Request For The Avengers
Although she may not remember, Gwyneth Paltrow appeared as Pepper Potts in Joss Whedon's 2012 film "The Avengers," a massive blockbuster that teamed up characters from five previous superhero movies into an ultra-powerful freelance military force. It was the third time Paltrow was in the film series, having appeared in "Iron Man" and "Iron Man 2" previously. In Jon Favreau's first "Iron Man," Pepper Potts and the title hero, played by Robert Downey, Jr., had a tempestuous professional relationship. Pepper capably and resentfully served as Tony Stark's personal assistant and as the chief wrangler of all his businesses. He, meanwhile, felt free to be an a-hole "genius maverick" who loved giving interviews in between bouts of drinking and hooking up.
Over the course of the "Iron Man" movies, Pepper and Iron Man grew closer and closer, revealing personal details about themselves and admitting a long-held attraction. It also helped that Tony went from being a blowhard lothario to being a superhero with a well-stated sense of righteousness. By the events of "The Avengers," Tony and Pepper were a proper couple who spent evenings in his Iron Man lab sipping champagne and looking warmly at each other (most people know that sex doesn't really exist in the Marvel Cinematic Universe).
It seems that the relationship between Tony and Pepper was a request by Downey. Whedon was quoted in a 2012 article by the Los Angeles Times as stating that Downey wanted Iron Man to have grown as a character in "The Avengers." Downey seemingly liked the character's flip dialogue and devil-may-care attitude, but he also felt that he should have grown up a little bit as well. That meant he was capable of having an adult, romantic relationship.
'Robert's thing'
The story for "The Avengers" was conceived by Whedon and longtime Hollywood superhero screenwriter Zak Penn (although Whedon received sole credit for the screenplay). It seems that they both took input from Downey, ostensibly the star of "The Avengers," alongside two handsome white men named Chris. The star seemingly had some say in how he wanted his character to be depicted. It was fair to listen to Downey's demands, as the success of the first "Iron Man" films might be chalked up to his affable charms and sense of humor. So when Robert Downey, Jr. says he wants Gwyneth Paltrow in "The Avengers" so that she and Tony Stark can be seen engaging in a healthy relationship, a director would be wise to listen. Whedon explained:
"But Pepper, this was really Robert's thing. He pushed hard. [...] He really thought Gwyneth would bring something great to the table, and we all thought so as well, but he was the one who convinced her to come and do it. [...] He didn't want to be sort of, crazy alone guy, he wanted to be crazy in-a-relationship guy."
Sadly, because of the secrecy surrounding a blockbuster bearing the magnitude of "The Avengers," there aren't many interviews from the time wherein Paltrow was able to give her views on the role she played. Indeed, it seemed she was required to keep her presence in the film largely secret; IGN quoted her as saying that she would only "possibly" appear in "The Avengers." Years later, Paltrow would admit that she never actually watched "The Avengers" and famously forgot she was in "Spider-Man: Homecoming."
It seems that Downey wanted Pepper Potts in the movie and that Whedon was willing to accommodate, but that Paltrow was indifferent one way or the other.