Sadie Sink plays Mary Jane Watson in a new 's story is a secret as of this moment, but even though Marvel and Sony have mostly kept quiet about the film's development, the first major casting update for the MCU movie came recently.

Sadie Sink has ed Spider-Man 4. The actress became known worldwide for her role as Max Mayfield in Stranger Things, one of the most popular characters on Netflix's flagship show. Her casting is exciting, and the fact that Sink's character has not been disclosed yet has led to many theories about who she could play. The casting report pointed at X-Men's Jean Grey, who Sink had previously been rumored to play in the MCU, as her Marvel character. However, it also teased that she could be playing Mary Jane Watson, and a new Spider-Man 4 theory makes her MJ's sister.

Zendaya’s MJ Will Reportedly Have A Minor Role In Spider-Man 4

Spider-Man: No Way Home Set That Up

While Marvel and Sony have yet to comment on the direction Spider-Man 4 is headed in, multiple reports about possible characters and storylines have emerged over the past year. Among them is the possible nature of MJ's role. Zendaya has already been confirmed to return for the film, with Holland saying that he read the MCU movie's script with her, and the two bounced around the room with excitement. However, Zendaya's MJ will reportedly have a reduced role in Spider-Man 4, which makes sense due to in-universe reasons and the actress' projects.

Spider-Man: No Way Home's ending paved the way for Zendaya's MJ and Jacob Batalon's Ned Leeds to play smaller roles if they appear in Spider-Man 4. The characters and the rest of the world forgot who Peter Parker was due to Doctor Strange's spell, with Holland's Marvel hero deciding not to remind MJ of their time together to keep her safe. Due to that, while Peter could bump into her in the MCU movie, MJ playing a major role would not make much sense. Zendaya also has a busy schedule in 2025 with Dune: Messiah, explaining her reduced role.

Spider-Man 4 Theory: Mary Jane And Michelle Jones Are Sisters

The MCU Could Go For Two Different Versions Of MJ At The Same Time

Zendaya's MJ does not make it impossible for Sink to play the MCU's Mary Jane Watson. After all, Marvel has made it very clear that the two are different characters, as Zendaya's MCU role is Michelle Jones, and her closed-off persona is nowhere near Mary Jane's outgoing personality. Even though Michelle received the MJ nickname Mary Jane is known for, effectively having her occupy the latter's role in the MCU's Spider-Man franchise, the two could co-exist. That is the driving force of a new Spider-Man 4 theory shared on Reddit by Randonanon4774 that explains how they could be sisters.

When MJ was questioned by the Department of Damage Control in Spider-Man: No Way Home, it was revealed that her full name was Michelle Jones-Watson. However, Zendaya's character claims she does not go by Watson. The Spider-Man 4 theory pulls from the comics, ing that Mary Jane has a complicated relationship with her father in them. The MCU could do a version of that, with Zendaya's MJ not keeping in touch with her father, who lives somewhere else with her estranged sister, Sink's Mary Jane. When Peter tries to look up MJ after Avengers: Doomsday, he finds Mary Jane instead.

How Spider-Man 4’s Possible Mary Jane Debut Is Better Through The Theory

The MCU Needs To Handle The Mary Jane Question Carefully

The theory is not the only way Sink could be introduced as Mary Jane. The character could come from another universe, given how the MCU's Multiverse Saga still rages on, and Spider-Man 4 will be released between the next two Avengers movies. Mary Jane Watson could also simply come from Earth-616, making her and Zendaya's MJ two different characters with no relation besides the MJ nickname. Zendaya has had to face some nasty comments over the years due to her playing the MCU's MJ, so introducing the "real MJ" now would not be a good look.

Even though she is called Michelle Jones, and her personality is nothing like Mary Jane's, it is clear that Zendaya's MJ has effectively served in the iconic character's role in the MCU's Spider-Man franchise. As such, if Sink is to play Mary Jane Watson, then putting a new twist to her story that ends up adding more depth to Zendaya's MJ is the way to go. The theory that Michelle Jones and Mary Jane are sisters is perfect due to that, and Tom Holland's Spider-Man 4 has the chance to make Sink's casting a major moment for MJ's character development.

All Announced MCU Movies

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  Thunderbolts*

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  The Fantastic Four: First Steps

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  Avengers: Doomsday (2026)

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  Spider-Man: Brand New Day

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  Avengers: Secret Wars

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