Marvel StudiosThere’s a lot that separates Marvel movies from “normal” movies. The biggest thing is, of course, the franchise itself, as each movie is the next chapter in an ever-growing saga. But Marvel Studios films also popularized the post-credits scene teaser, as well as surprise cameos that lead into other movies or shows. But one other surprising filmmaking technique has been part of the Marvel Cinematic Universe fabric from the beginning.Many fans are shocked to hear that Marvel movies are often filmed without a finished script, with scenes added throughout the shooting process. This is very unusual — on the other side of the spectrum over at DC Studios, James Gunn makes it a point to have a finished script before all else and often doesn’t need reshoots at all. But the Russo brothers, the directors of the upcoming Avengers: Doomsday, have defended their choice, saying it allows for more cooperation. The Russos see their constantly evolving scripts as a feature, not a bug. | John Salangsang/Shutterstock“We always view the script as a living organism,” Joe Russo told the AP. “We’re improvisation-based, rehearsal-based directors. We like to see what the actors bring to the characters, and sometimes you don’t get the actors until a few days or few weeks before you shoot them. And a lot of the time, that’s when the magic happens.”This is a technique referred to at Marvel as “plus-ing.” Kevin Feige discussed the method with The Hollywood Reporter in July 2025. “There’s plus-ing happening every day on the Avengers: Doomsday set right now, and it is amazing to watch because what those filmmakers, those actors, both the ones that are playing these characters for the first or second time and the one playing them for the 10th or 12th time, are the best in the world at it, and know these characters so well,” he said. “So if they have an idea, you want to listen to it and you want to adjust to it and you want to improve it. I wouldn’t want to change that.” Kevin Feige defends the use of “plus-ing” on the set of Doomsday. | CHRIS TORRES/EPA/ShutterstockSo is this a method that actually works? In a way, it’s one that laid the foundation for the MCU itself: Iron Man reportedly began shooting with just an outline and no finished script; it was mostly written on the fly by director Jon Favreau and stars Robert Downey Jr. and Jeff Bridges (at least, according to Bridges). Miraculously, Iron Man came together and launched the MCU as we know it, so perhaps it could work once again for the Russos with Doomsday.But it’s been a while since we’ve seen a Russo-directed Marvel movie, and Doomsday has a huge cast, so having a clear script will be more important than ever. The true success will need to come with Doomsday. If it’s as clear and concise as, say, DC’s Superman, then that proves this collaborative process actually works. But if the story gets muddled, there may be too many cooks in the kitchen, which bodes poorly for Avengers: Secret Wars next year. The Russos do have a lot of history with on-set improvisation, as they established themselves directing comedy shows like Community and Arrested Development. But when it comes down to it, Doomsday is uncharted territory, and is the most ambitious Marvel movie yet. Maybe this is the limit to this unorthodox technique. Avengers: Doomsday premieres in theaters on December 18, 2026.