This Avengers: Doomsday theory suggests that X-Men Days of Future Past may have created Robert Downey Jr.'s Doom

Following Marvel's furniture-focused livestream, which revealed some big cast names headed for Avengers: Doomsday, all manner of theories have flooded onto the internet in an effort to anticipate how Robert Downey Jr.'s Latverian lunatic in a different kind of armor will impact the MCU.

One grim theory suggests that the order in which the cast is revealed may indicate the order in which they will die in the film, with Doctor Doom defeating the God of Thunder first and demonstrating just how powerful a threat he poses to our heroes. However, a new theory from Screen Rant's Liam T. Crowley on X proposes an idea regarding the appearances of some of the original X-Men cast, including Kelsey Grammer, Patrick Stewart, James Marsden, Ian McKellen, and Alan Cumming, which may stem from the aftermath of the beloved comic book movie, X-Men: Days of Future Past. On X, Crowley wrote "Grammer. Stewart. McKellen. Cumming (ha). gotta be the fox universe. the one that reversed the sentinels shit. 'you mess with time it tends to mess back.' did reversing the events of days of future past create downey doom?? stay with me now!!"

At the end of the 2014 film, the joint effort from mutants across time stopped the extinction of their kind while also resetting the timeline to a brighter future for the world's Wolverine (Hugh Jackman). In doing so, he's reunited the likes of Cyclops (James Marsden), Jean Grey (Famke Janssen), Beast (Grammer), and Charles Xavier (Patrick Stewart). A job well done, right? Well, what if, according to Crowley, the rectifying of time brought about Downey's approaching Doom, who makes his way across realities into the MCU? As Tony said in Avengers: Endgame, "When you mess with time, it tends to mess back," which could include the repercussions of fixing the Days of Future Past timeline.

It would certainly be a clever way to cross over into both franchises and do so with an event that tampered with time long before the Avengers even got the idea. That being said, there's also a chance that these X-Men could all be different variants, just like how Deadpool & Wolverine homed a different variant of Logan (Hugh Jackman) from the one we spent 17 years with. All of these returning cast members could be playing different iterations of the characters we've known for decades (we already saw a Charles snuff it in Doctor Strange in the Multiverse of Madness, after all), perhaps even the ones we've been reacquainted with in X-Men '97.

We'll have to wait and see which X-Men and other mutants we'll meet when Avengers: Doomsday arrives in theaters on May 1, 2026. Also, keep tabs on every upcoming Marvel movie and TV show planned for the future here.