Marvel Studios' first wave of cast reveals for Avengers: Doomsday included several of the OG Fox X-Men, including Kelsey Grammar as Beast, James Marsden as Cyclops, Rebecca Romijn as Mystique, Alan Cumming as Nightcrawler, Patrick Stewart as Professor X, and even Ian McKellen as Magneto, along with the addition of Channing Tatum's Gambit.

Stewart and McKellen’s return as Professor Charles Xavier and Magneto signifies a remarkable reunion for the X-Men legacy. With Stewart last seen in Doctor Strange in the Multiverse of Madness and McKellen in X-Men: Days of Future Past,

Men" featuring Patrick Stewart as Professor Charles Xavier, Ian McKellen as Magneto, Alan Cumming as Nightcrawler, Rebecca Romijn as Mystique and James Marsden as Cyclops, are set to return in "Avengers: Doomsday,

However, other fans think that Avengers: Doomsday will involve a timeline incursion that will merge the Fox X-Men timeline with the current main Earth 616 timeline, just like Deadpool and Wolverine did. "There's multiple incursions going on," pointed out another fan. "There's definitely the one that Dr Strange caused."

Marvel has announced the return of some Marvel Cinematic Universe (MCU) stars in 2026's "Avengers: Doomsday," including Chris Hemsworth as Thor, Anthony Mackie as Captain America, Sebastian Stan as Bucky Barnes and Tom Hiddleston as Loki.

The Fantastic Four cast, Chris Hemsworth, Simu Liu, a bunch of X-Men, and more will battle Robert Downey Jr.'s Doctor Doom in Avengers 5. Marvel Reveals Avengers: Doomsday Cast, Including Patrick Stewart, Ian McKellen, Channing Tatum Ben Kaye

He’ll always be my Magneto—the one who understood the true nature of power and how easily it could be abused. With Avengers: Doomsday, we’re expecting nothing less than a magnetic performance (pun intended) as Magneto wrestles with the idea of joining forces with his old friend, Charles Xavier.

Robert Downey Jr. returns to the MCU with other confirmed actors including stars Chris Hemsworth and Tom Hiddleston, 'X-Men' stars like Patrick Stewart and Ian McKellen, and a good chunk from the studio's 'Thunderbolts.