Sadie Sink officially made her long-awaited debut in the Marvel Cinematic Universe when Spider-Man: Brand New Day arrived in theaters on July 31. The Stranger Things star received rave reviews for her performance, with fans and critics all praising her as the show-stealer in the film's third act. And, honestly, it's hard to argue with that.
After such mystery and intrigue surrounding the character she was playing (which we will reveal shortly!), it's been incredibly fulfilling to see her thrive, knowing that she's set to be a part of the MCU franchise for many more years to come. The question is: Will her next chapter in that franchise come in Avengers: Doomsday? That's a little more complicated to anticipate, but there is some evidence to suggest that it won't be the case.
*** Before we go on, we should warn you that this article features MAJOR SPOILERS from Spider-Man: Brand New Day, including the identity of who Sadie Sink is playing in the MCU. Don't read on if you haven't seen the movie and would prefer it wasn't spoiled for. ***
Sadie Sink's impression on moviegoers is just the beginning for not just her, but seemingly for the X-Men in general, as the MCU heads towards its long-awaited X-Men reboot - and what is tentatively being referred to as the "Mutants Era". But while that Mutants Era seemingly won't begin until after Avengers: Doomsday comes out, there will be a reason for X-Men fans to tune in.
Why Sadie Sink isn't in Avengers: Doomsday
Sadie Sink's MCU debut as Jean Grey sent the internet into a meltdown, which is pretty darn impressive considering that a lot of the long-standing Marvel fans were predicting that she might play the iconic X-Men character. But no, even the rumor mills and insider reports couldn't take away the collective chills that audiences around the world felt when Peter Parker first uttered those words: "Jean Grey".
Jean is obviously set to be a major part of the MCU going forward, but we shouldn't expect that to officially begin in Avengers: Doomsday. Marvel has big plans for the character in its next era, which will center on the upcoming X-Men reboot movie - placing Marvel's Mightiest Mutants at the core of the next Saga. However, before all of that, it has to wrap up the Multiverse Saga. And that's where Avengers: Doomsday comes in.
As it stands, Sink is not a part of the main cast of Avengers: Doomsday. Her name was not listed among that initial five-hour livestream that revealed which Marvel returnees would be taking part in the larger-than-life ensemble film and there have been no subsequent announcements about her involvement since. While that doesn't necessarily rule out a cameo appearance from Jean Grey, that would be much more effective in 2027's Avengers: Secret Wars - which is designed to close out the Multiverse Saga and set the stage for the next one: The Mutants Era.
Doomsday is the opening salvo to a much bigger battle in Secret Wars. She could theoretically be involved in that one, but with a confirmed group of Avengers, a core mission to stop Doctor Doom, and an inevitable cliffhanger ending that will seemingly see the heroes temporarily fail, there is little reason to expect Jean to make an appearance in this one. That doesn't, however, mean that X-Men fans shouldn't tune into it!
The original X-Men return in Avengers: Doomsday
If you're holding out hope for appearances from Sadie Sink's Jean Grey, Kit Connor's Cyclops, or any of the other new X-Men stars of the MCU in Avengers: Doomsday, there is one particularly big reason as to why that likely won't be happening: The original X-Men stars are coming back in this one.
That's right; back when Marvel Studios announced the cast for the upcoming film via that five-hour livestream, there were some expected but major announcements. We obviously knew that the likes of Chris Hemsworth, Florence Pugh, Sebastian Stan, Anthony Mackie, Pedro Pascal, Vanessa Kirby, Tom Hiddleston, Wyatt Russell, and Robert Downey Jr. would be among the returnees. What we didn't expect was for the likes of Sir Ian McKellen, Sir Patrick Stewart, James Marsden, Rebecca Romijn, Alan Cumming, and Kelsey Grammer to be among the cast.
All of these stars will reprise their roles from Fox X-Men movies of the 2000s and 2010s, with McKellen and Stewart bringing back Magneto and Professor Charles Xavier, Marsden returning as Cyclops, Romijn as Mystique, and Cumming and Grammer back as Nightcrawler and Beast, respectively. Needless to say, this is a very big deal.
Now, there are some notable absences: Famke Janssen's Rogue, Halle Berry's Storm, and Anna Paquin's Rogue were also additions that fans would have loved to see. Even Hugh Jackman's Wolverine - who made his return to screens after nearly a decade away from them in MCU film Deadpool and Wolverine (and is expected to remain a part of the franchise for years to come) wasn't announced as part of the cast.
All that being said, fans are extremely excited at the prospect of seeing at least some of the original X-Men stars back on our screens - especially as they will be donning their signature comic-accurate suits for the very first time ever. And this, in a way, is an attempt to right a wrong from years ago, rewarding the OG X-Men with the honor they should have been allowed in their era in what is expected to be a send-off to the legendary franchise stars in Avengers: Doomsday.
This not only familiarizes MCU audiences with the X-Men characters ahead of the reboot in 2028, it allows us to these the original X-Men legends one more time.
With that in mind, Avengers: Doomsday remains a must-watch for X-Men fans. The only question we have left to ask is: Is it December yet?
Avengers: Doomsday arrives in movie theaters on December 18, 2026.
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