Since Sadie Sink joined the cast of the upcoming Spider-Man: Brand New Day movie, many fans of Marvel Studios have been wondering about one of the biggest secrets of this movie. In fact, even though Marvel Studios did not reveal anything about the role of the young actress, there are many fan theories circulating about who she is. As of yet, neither Marvel Studios nor Sadie Sink herself has revealed any information about who she will be in the movie, and Destin Daniel Cretton mentioned that there is a good reason why it should be kept a secret.
Jean Grey Is the Leading Theory
Most popular among them is the assumption that Sadie Sink plays the part of Jean Grey, one of the most famous X-Men characters in the Marvel universe. The theory became especially popular after Marvel fans saw signs in the advertising campaign and it was reinforced when musician Steve Lacy alluded to the name "Jean" when talking about the movie at its premiere. Those who are backing this theory say that the inclusion of Jean Grey will be a big step toward the complete integration of the X-Men into the Marvel Cinematic Universe. Yet Marvel hasn't confirmed her presence yet.

Could She Be Gwen Stacy?
Another popular theory involves Gwen Stacy, one of the favorite characters from the Spider-Man comics. Considering that Brand New Day represents a brand-new chapter for the life of Peter Parker after Spider-Man: No Way Home, some viewers think that introducing the new Gwen makes sense in the storyline. Still, there has not been any confirmation from Marvel regarding the inclusion of Gwen into the plot of the movie. The theory has emerged primarily because of the popularity of the character in the Spider-Man comics and the age of Sink.
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Other Popular Fan Theories
Besides Jean Grey and Gwen Stacy, there are many other names that have been floating around the internet. Some of the suggestions from fans include Sink playing Mayday Parker, who is the future daughter of Peter Parker in the Marvel Comics. Others have included suggestions like Mary Jane Watson or Rachel Summers. All of these are suggestions from the comic books because there is nothing official from Marvel Studios yet.

Why Marvel Is Keeping the Role Secret
Marvel Studios has heightened the anticipation by not disclosing who Sadie Sink will play in the movie through teasers and even interviews. It is evident through what Kevin Feige has revealed about the importance of Sadie Sink’s casting to the story development of the film, and Tom Holland has also commended her without saying her role. The mystery has become one of the ways of marketing the movie, making the fans analyze everything from teasers and interviews for hints. Regardless of whether Sadie Sink ends up playing Jean Grey, Gwen Stacy, or an entirely different character altogether, it will be known once the movie Spider-Man: Brand New Day comes out.
Final Take
The part played by Sadie Sink in the Spider-Man movie titled “Brand New Day” is still one of Marvel’s most secret things ever. Even though Jean Grey still dominates in the minds of fans, there are several theories relating to other comics characters like Gwen Stacy, Mayday Parker and others that are yet to be confirmed.
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