5 Shocking Characters Sadie Sink Could Be Playing In Spider-Man 4 (The Ultimate Casting Mystery)

The internet is buzzing with one of the biggest casting mysteries of the year, as of December 15, 2025: Is Stranger Things star Sadie Sink officially joining the Marvel Cinematic Universe (MCU) alongside Tom Holland's Peter Parker? Multiple reports from major trades and industry scoopers suggest that the actress is indeed set to appear in the next installment, widely rumored to be titled Spider-Man: Brand New Day. The only question that remains is who she will play, a secret so tightly guarded it has fueled a massive, multi-character fan casting frenzy across the web.

This rumored casting has instantly become a focal point for the future of the MCU's Spider-Man saga, which needs a new romantic and emotional anchor following the events of Spider-Man: No Way Home. Sadie Sink, known for her powerful, Emmy-nominated performance as Max Mayfield, brings a level of dramatic gravitas and star power that could redefine a classic comic book role. From the obvious redheaded choice to a shocking X-Men crossover, here is everything you need to know about the intense speculation surrounding Sadie Sink's top-secret role.

Sadie Sink: A Brief Biography and Profile

Sadie Sink has quickly risen from a Broadway prodigy to a global phenomenon, primarily due to her work on Netflix's flagship series, Stranger Things. Her career trajectory demonstrates a clear capacity for complex, emotionally charged roles, making her a compelling choice for a major MCU character.

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• Full Name: Sadie Elizabeth Sink
• Date of Birth: April 16, 2002
• Place of Birth: Brenham, Texas, U.S.
• Age (as of 2025): 23
• Breakout Role: Max Mayfield in Stranger Things (Seasons 2–5)
• Notable Filmography:
  • The Whale (2022) - Ellie (Received critical acclaim)
  • All Too Well: The Short Film (2021) - Her (Taylor Swift's short film)
  • Fear Street Part Two: 1978 (2021) - Ziggy Berman
  • The Glass Castle (2017) - Young Lori Walls
• Broadway Career:
  • Annie (2012–2014) - Annie
  • The Audience (2015) - Young Queen Elizabeth II
• Awards/Nominations: Critics' Choice Movie Award nomination, Screen Actors Guild Award nominations, and an Emmy nomination for Stranger Things (pending confirmation of latest awards cycle).

The Leading Contender: Mary Jane Watson (MJ)

The most persistent and visually obvious rumor is that Sadie Sink will take on the iconic role of Mary Jane Watson, Peter Parker's most famous and enduring love interest.

The Case for Mary Jane Watson

For decades, Mary Jane has been synonymous with her fiery red hair and famous catchphrase, "Face it, Tiger... you just hit the jackpot." Sadie Sink’s natural look aligns perfectly with this classic comic book depiction, which was notably absent in the MCU’s previous trilogy starring Zendaya as "MJ" (Michelle Jones-Watson).

• Comic Accuracy: Fans have long clamored for a comic-accurate MJ, and Sink fits the visual profile perfectly.
• A Fresh Start: Following the mind-wipe at the end of No Way Home, Peter Parker is a clean slate. Introducing Mary Jane as a new, major figure in his life would perfectly align with the rumored "Brand New Day" title—a comic arc where Peter's life is reset.
• Industry Scoops: Reputable industry insiders, including Jeff Sneider, have reported that Sink is set to play MJ in Spider-Man 4.

The Counter-Argument and Sink's Hint

Despite the strong visual match, Sadie Sink herself has hinted that fans might be overthinking the hair color connection. In a recent statement regarding the casting speculation, she suggested that "Hair colour can change," and that "people will just have to wait and see." This quote has thrown the entire speculation wide open, suggesting her role might be a character not traditionally known for being a redhead.

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The Ethereal Favorite: Gwen Stacy (Spider-Gwen)

The second most powerful rumor, and perhaps the one generating the most complex theories, is that Sadie Sink is being cast as Gwen Stacy, a character previously seen in the Amazing Spider-Man films and, more recently, as the beloved Spider-Gwen in the animated Spider-Verse.

Why Gwen Stacy Makes Sense in the New MCU

Gwen Stacy's character arc is often defined by tragedy and a deep, intellectual connection with Peter Parker. After the dramatic events of No Way Home, Peter is alone and isolated, making a new, profound relationship a narrative necessity.

• The Emotional Arc: Sink's ability to portray deep, internalized pain (as seen in The Whale and Stranger Things) makes her an ideal candidate to handle the complex, often tragic, storyline associated with Gwen Stacy.
• Multiverse Potential: While Gwen Stacy's main MCU counterpart has not been introduced, the possibility of a Multiverse variant—perhaps a live-action Spider-Gwen—is a major fan theory, especially with the upcoming Avengers: Secret Wars.
• The "Brand New Day" Connection: The introduction of Gwen Stacy would signal a definitive new chapter for Peter, moving past the MJ relationship that the world has forgotten.

The Wildcard Rumors: Mayday Parker and Jean Grey

While Mary Jane and Gwen Stacy dominate the discussion, two other characters have been consistently mentioned in the latest 2025 rumors, demonstrating the sheer breadth of the mystery role.

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Mayday Parker (Spider-Girl)

Some reports have suggested that Sadie Sink could be playing Mayday Parker, who is the daughter of Peter Parker and Mary Jane Watson from an alternate future timeline in the comics, where she becomes the hero Spider-Girl.

• The 'Brand New Day' Twist: Casting her as Mayday would be a major twist, potentially setting up a new, younger generation of heroes for the MCU.
• The Age Factor: At 23, Sink is still young enough to play a high school or college-aged character, fitting the typical age of a newly introduced hero.

Jean Grey (X-Men Crossover)

Perhaps the most shocking rumor links Sadie Sink not to the Spider-Man universe, but to the X-Men. Some sources have claimed she is cast as a young Jean Grey, the powerful telepath and telekinetic mutant.

• MCU Integration: This theory is based on the idea that Spider-Man 4, and the rumored Brand New Day title, will be a soft launch for the introduction of mutants into the MCU. The trades initially mentioned Jean Grey as a possibility when the casting news first broke.
• Reprise in Secret Wars: This rumor is bolstered by separate reports that Sink will reprise her top-secret role in the massive crossover film Avengers: Secret Wars, where the X-Men are heavily expected to play a part.

The Final Verdict on Sadie Sink's MCU Role

As of late 2025, the casting of Sadie Sink in Spider-Man 4 remains one of the most exciting and tightly guarded secrets in the MCU. While the sheer volume of speculation points to a major, redheaded character—most likely Mary Jane Watson or Gwen Stacy—Sink’s own cryptic comments suggest Marvel may be planning a surprise that breaks from fan expectations.

The decision to cast an actress of Sink’s caliber in a mystery role is a strategic move by Marvel, designed to maximize curiosity and discussion. Whether she utters the words "Face it, Tiger," swings into action as Spider-Gwen, or introduces the X-Men, one thing is certain: Sadie Sink’s arrival in the MCU will mark a definitive "Brand New Day" for Tom Holland's Peter Parker.