Marketing for The Marvels sneakily included an X-Men tease from the get-go after the letter "X" was highlighted for an extra beat during one promo, indicating the mutants' arrival to the wider MCU.
Warning - the rest of this article contains spoilers for The Marvels.
After Monica Rambeau seemingly sacrificed herself by closing the breach to save the universe, the sequel's post-credits scene revealed that she ended up in an alternate universe where the X-Men exist, and her mother, Maria, is Binary.
Not long after that, Beast entered the room to tell Monica that she's now a parallel reality before leaving to give Charles Xavier an update about what's going on.
Who is Kelsey Grammer's Beast In the Marvel Universe?
In Marvel Comics, Beast, aka Hank McCoy, is a mutant who is transformed into a blue-furred creature with fangs and claws after developing a serum that he thought was a cure to his mutation.
Despite his unusual physical appearance, Beast is highly intelligent and he has a superhuman physique, strength, and durability.
Kelsey Grammer (Cheers, Frasier) made his Marvel debut as Hank McCoy in 2006's X-Men: The Last Stand. In the movie, McCoy is a member of the U.S. Cabinet as the Secretary of Mutant Affairs.
Beast had a prominent role in the X-Men threequel, with him fighting for the peaceful coexistence between mutants and humans.
After learning about a mutant boy named Leech who has the ability to suppress mutant powers, Beast eventually told Charles Xavier and the X-Men all about it, much to their disdain.
McCoy eventually resigned from his position after he became upset that the mutant policy of weaponizing the cure was made without his input. He later rejoined the X-Men's fight against Magneto and the Brotherhood of Mutants.
After successfully defeating Magneto, Beast became the U.S.'s new ambassador to the United Nations – a representative for humans and mutants alike.
X-Men: The Last Stand wasn't Grammer's only appearance in the movies since he also appeared in a brief cameo at the end of 2014's X-Men: Days of Future Past as a professor in Charles Xavier's school.
Grammer wasn't the only actor who played Hank McCoy in Fox's X-Men movies since Nicholas Hoult (Warm Bodies, The Menu) portrayed a younger version of the character in X-Men: First Class, X-Men: Days of Future Past, X-Men: Apocalypse, and X-Men: Dark Phoenix.
What's Next for Kelsey Grammer's Beast in the MCU?
Despite his brief appearance, The Marvels' post-credits scene heavily teased that Kelsey Grammer's Beast will play a much more significant role in at least one future MCU movie, especially now that an important Earth-616 character like Monica Rambeau is in their universe.
At this point, it remains to be seen if Grammer's version of Beast who appeared in the post-credits scene is the same one who was featured in X-Men: The Last Stand and X-Men: Days of Future Past.
It's possible that he could be the same version, and could even be the one from the restored timeline in Days of Future Past where everyone is alive.
Still, given that Doctor Strange in the Multiverse of Madness established that Patrick Stewart's Charles Xavier is a completely different Variant, there's the likelihood that Grammer's Beast in The Marvels is a unique version as well.
The Marvels' post-credits scene revealed that Beast is completely aware of the Multiverse, and this could be a starting point of how he will help Monica to get back home to her universe.
With the threat of the Kang Variants looming in the background, Monica could even recruit Grammer's Beast, Binary, and the rest of the X-Men in the fight for the Multiverse when the time comes.
The Marvels is now playing in theaters worldwide.