Feige elaborated that "much of the movie will still be based very much on [Wright and Cornish's] draft and the DNA of what Edgar has created up to this point", with Reed stepping in to direct and McKay reworking only parts of the script. "[Reed] wanted to be sure that he wasn't just inheriting something or following someone else's lead. Or wasn't inheriting something that the evil studio had watered down to be something bad," Feige continued. "He looked at everything, he talked with us, and he said 'Number one, I agree with the direction you're going in. And number two, I can add to it.'"
McKay stated that Rudd helped him rewrite the script, calling Rudd "great with dialogue", adding "the two of us holed up in hotel rooms on the east and west coast, and I think it was like six to eight weeks we just ground it out and did a giant rewrite of the script. I was really proud of what we did, I really thought we put some amazing stuff in there and built on an already strong script from Edgar Wright and sort of just enhanced some stuff." Rudd elaborated, "The idea, the trajectory, the goal, and the blueprint of it all, is really Edgar and Joe. It's their story. We changed some scenes, we added new sequences, we changed some characters, we added new characters. If you took the two scripts and held them up together they'd be very different—but the idea is all theirs."Reed also offered contributions to the revised script, as did Lilly and Stoll, who contributed ideas to help flesh out their respective characters. Lilly's character received a fuller arc and more action sequences as a result. One of the important things when joining the film for Reed was emphasizing both Hope and Janet van Dyne more, given the Wasp being "a crucial part" of the Ant-Man comics. For their efforts, McKay and Rudd were credited as additional writers of the screenplay, with Wright and Cornish credited for the screenplay and story. Wright also held an executive producer credit on the film.