In 2024, it was announced that Doctor Doom will be played in the movie – and its 2027 follow-up Avengers: Secret Wars – by Robert Downey Jr, who previously portrayed Iron Man in the Marvel Cinematic Universe. The "Nobody 2" actress got an Oscar nomination for her role in the classic Martin Scorsese movie, but it wasn't easy to film.

It speaks to how stacked Avengers: Doomsday's cast currently is that Cyclops actor James Marsden returning to his iconic X-Men role for the first time in over a decade has barely been a topic of conversation ahead of the MCU crossover event.

One of the original X-Men actors from Fox's Marvel movies finally opens up about making their Marvel Cinematic Universe debut in Avengers: Doomsday.