Avengers: Endgame scribes Christopher Markus and Stephen McFeely say they restricted their use of the super-powerful Captain Marvel (Brie Larson) because it would have been "unfair" to the original six Avengers to have an outside character "come in and solve all their problems."
"She was always going to be in it, but we didn't have much to go on. They had cast her, and that was it," Markus told Vanity Fair. "It is a tough balance to strike when you have a character that powerful, who you're going to bring in, and you don't want it to seem like, 'Well, we just brought in this person who can clean the house, that we couldn't [have] clean in the previous movie.' So we had to decide on a balance between not making it feel like a cameo, but not having her around so much that she solved all the problems for everybody."
Added McFeely, "It also wasn't the point of the movie."
"The point of the second movie was saying goodbye to the original six Avengers, so their stories were gonna be way up here," McFeely continued. "We had the same issue a little bit with Black Panther in Infinity War because people go, 'Oh! Black Panther, he's coming back two months from now! Alright, I'm gonna get a lot of Black Panther!' And he got some. I mean, we went to Wakanda, but he wasn't the lead character. It was not fair to the other six Avengers to have Captain Marvel come in and solve all their problems. It didn't seem like good storytelling."
Markus and McFeely also had the unique challenge of scripting a character who first filmed on Endgame before her own solo movie under directors Anna Boden and Ryan Fleck.
"We sat with them and showed them the [Endgame] draft and said, 'Here's how she works in our movie, and here's how she sounds. Do you think this version of her, which is a version we had to decide on for our movie, which is 20 years after the hypothetical movie you're going to make — have we done anything that would force you to do anything you didn't want to do previously?'" McFeely previously told Backstory Magazine. "It was fine, but we certainly got their input."
The Avengers writers did review the Captain Marvel script during filming on Endgame, but according to Markus, "It was informative, but if anything, it was too late to make any changes to ours."