Marvel Studios’ major cast announcement has definitely supported one of my biggest theories for Avengers: Doomsday. Set to release in 2026, the fifth Avengers movie is set to feature a vast collection of MCU characters, and likely even more than the 27 who were confirmed during Marvel’s recent live stream event. That said, the characters we now know will be featured have led me to believe that Doomsday is set to tackle a lot more than just a battle with Robert Downey Jr.’s Doctor Doom.

During the 5-and-a-half-hour live stream event from Marvel Studios, a large portion of the cast for Avengers: Doomsday was confirmed with the revealing of each actor’s chair with their name on it. While this included some expected names like Anthony Mackie (Captain America) and Chris Hemsworth (Thor), there were also some very exciting actors confirmed who’ve historically played Marvel characters not native to Earth-616, the primary MCU reality. To that end, I’m pretty confident about my biggest Avengers: Doomsday theory and how it will involve the X-Men.

Marvel Just Announced Multiple X-Men For Avengers: Doomsday

Professor X, Magneto, Gambit, and More!

In The Marvels’ post-credits scene, Monica Rambeau meets Kelsey Grammar’s Beast in another reality apart from the main MCU that’s home to the X-Men. Combined with 2024’s ᴅᴇᴀᴅpool & Wolverine and its confirmation that Fox’s X-Men universe was Earth-10005 and a part of the greater multiverse, I’ve been theorizing about some level of X-Men involvement in Doomsday and Secret Wars for some time now. However, this new casting announcement has blown my previous expectations out of the water, while also supporting a theory I’d previously thought was kinda out there.

Not only did Kelsey Grammar get a chair in the live stream, confirming his return as Beast, but Patrick Stewart’s Professor X and Ian McKellan’s Magneto were surprisingly confirmed for Avengers: Doomsday as well. Likewise, Fox’s original Mystique and Nightcrawler actors (Rebecca Romijn and Alan Cumming) were confirmed, as was James Marsden’s Cyclops and Channing Tatum’s Gambit, who finally made his debut last year in ᴅᴇᴀᴅpool & Wolverine. This brings the current total of X-Men appearing in Avengers: Doomsday to seven (though there will likely be even more than that).

I Think Fox’s X-Men Universe Is Going To Replace The Ultimate Universe

Remixing Marvel Comics’ Final Incursion Before 2015’s Secret Wars

All in all, it seems as though Fox’s X-Men universe will be more involved in Avengers: Doomsday than most people initially realized. However, I’ve long had the thought that the X-Men universe could very well replace the Ultimate Universe’s role as the MCU looks to adapt elements from the comics’ Secret Wars event. In the 2015 crossover, the main Marvel reality and the Ultimate Universe (Earth-1610 aka the home of Miles Morales) were the last two Earths in the multiverse that hadn’t yet been destroyed via incursions.

As these last two worlds collided with the promises of nothingness in the aftermath, it was Doctor Doom who created Battleworld in the comics, a patchwork plane of existence made from the fragments of various destroyed realities with the help of Molecule Man and Doctor Strange. As such, many are expecting the MCU to follow suit with RDJ’s Doctor Doom creating Battleworld, making himself God Emperor Doom in Avengers: Secret Wars. However, Avengers: Doomsday can be the prelude event, where Earth-616 and Earth-10005 are the last two worlds in the multiverse following multiple incursions.

Theory: Doomsday Is Really An Avengers vs. X-Men Multiverse Movie

“Avengers ᴀssemble” vs. “To Me, My X-Men”

If the above idea is proven correct, it means Avengers: Doomsday is essentially a secret Avengers vs X-Men film, which just so happens to be the only other idea the Russos said years ago they’d might return to the MCU for besides Secret Wars. Now, it certainly looks as though the stage is set for the Russos to do both, albeit with the Avengers vs. X-Men concept having more of a multiversal twist fighting for survival, rather than the two teams battling over the Phoenix Force in the original comics.

At any rate, it would be very cool to see the Avengers and X-Men pitted against each other for the sake of their respective worlds’ existence, at least before Doom arrives to “save” the day. Likewise, this also ties nicely with The Leader’s comments in Captain America: Brave New World’s post-credits scene when he tells Sam Wilson that “other worlds/heroes” would soon have to be reckoned with. All in all, the odds seem quite high that the Avengers will soon have to fight the X-Men in the MCU, especially if Avengers: Doomsday adds even more mutants to its cast.

Avengers: Doomsday releases in theaters on May 1st, 2026.

Upcoming MCU Movies

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  Captain America: Brave New World

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  February 14, 2025
  

  
  
  
  

  
  

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  Thunderbolts*

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  May 2, 2025
  

  
  
  
  

  
  

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  The Fantastic Four: First Steps

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  July 25, 2025
  

  
  
  
  

  
  

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  Avengers: Doomsday (2026)

  
  
  
  
  

  
  

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  MCU Spider-Man 4

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  July 24, 2026
  

  
  
  
  

  
  

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  Avengers: Secret Wars

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  May 7, 2027
  

  
  
  
  

  
  

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