While Ant-Man was one of the first feature film projects that Marvel Studios began developing, it went through some rather dramatic changes just months before finally starting production this summer. Filmmaker Edgar Wright had been developing the movie for years, writing the screenplay with Joe Cornish and even casting the majority of the roles, but he left the project a few months before production over creative differences with Marvel. The studio worked quickly to keep the project together and eventually signed Peyton Reed to direct, but before that Anchorman and Step Brothers director Adam McKay briefly flirted with the director’s chair. While McKay subsequently opted not to take the helm, he did agree to come onboard as a screenwriter, fine tuning the script in the months leading up to the start of filming.

Steve recently spoke with McKay in anticipation of the upcoming short film series We the Economy: 20 Short Films You Can’t Afford to Miss, and during the course of their conversation McKay talked a bit about his involvement with Ant-Man. Paul Rudd told us at Comic-Con that he had been working with McKay “every day for six weeks” on the Ant-Man script, and McKay confirmed as much in this new interview, elaborating on how he got involved in the project and his initial apprehension. McKay also discussed the nature of the rewrite, saying they added some action beats and made the script “a little bigger, a little more aggressive, and funnier in places.” Much more after the jump.

Speaking with Steve, McKay detailed how he first got involved in Ant-Man:

“[Rudd] called me when Edgar Wright stepped away from the project and told me what was going on. I went and met with Marvel, and I was a little dubious just because I’m friends with Edgar and I didn’t know what the story was, and then when I kind of heard what happened, that Edgar had parted ways, and then I saw their materials, I was like, ‘God this is pretty cool’. Ultimately I didn’t want to jump in as a director, I had too many other projects going and it was too tight, but I thought, ‘You know what, I can rewrite this, and I can do a lot of good by rewriting it.’”

McKay confirmed that he and Rudd worked on the script together, and said that he was surprised by Rudd’s talent for dialogue:

“I’ve always known Paul Rudd’s a really good writer from improvising with him on set, but I had no idea he was that good—he’s really great with dialogue. So 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.”

With Wright leaving the project so close to production, many of the action set pieces had no doubt already been storyboarded and pre-visualized, but McKay says the amount of Wright’s action beats versus the amount of new action beats in the finished film is “half and half”:

“We added some new action beats. I grew up on Marvel Comics so the geek in me was in heaven that I got to add a giant action sequence to the movie; I was so excited. So we did, we added some cool new action. There’s a lot that’s already in there from what Edgar did, there’s a lot of dialogue and character still in there.

As for what, specifically, McKay and Rudd added to the script, McKay says it was a matter of streamlining the story and expanding the scope:

“We just shaped the whole thing, we just tried to streamline it, make it cleaner, make it a little bigger, a little more aggressive, make it funnier in places—we just basically did a rewrite. Edgar had a really good script. But we just had a blast, and Rudd was just so much fun to write with. I walked away saying, ‘Hey, you and I gotta write a script together.’”

Watch the portion of Steve’s interview with McKay regarding Ant-Man below, and look for the full interview on Collider soon.