Sadie Sink Isn’t Done With the MCU After Tom Holland’s Spider-Man: Brand New Day

Sadie Sink is swinging into the MCU with Spider-Man: Brand New Day, and Marvel is doing that classic Marvel thing: telling us she is in the movie with Tom Holland, then refusing to say who she plays. The secrecy is already the story, and the rumors are doing laps.

What is actually on the board right now

• Sadie Sink will appear in Spider-Man: Brand New Day alongside Tom Holland. Marvel has not announced her character.
• There is chatter that her role could continue into Avengers: Secret Wars after Brand New Day (Deadline has floated this), but Marvel has not confirmed any connection.
• Spider-Man: Brand New Day is dated for a worldwide theatrical release on July 31, 2026.
• The current Secret Wars talk has it arriving December 17, 2027, with the Russo Brothers reported as directors and names like Joseph Quinn, Vanessa Kirby, Pedro Pascal, and Robert Downey Jr. in the mix. None of that is locked by Marvel, so treat it as in-pencil, not in-ink.

So who is Sink playing? Here are the workable angles

The boring-but-likely option: Marvel keeps her in the Spider-Man lane at first. Think a character built for Peter Parker's world who could pop up again if the vibes are right. Marvel likes to test-drive new pieces inside single corners of the sandbox before merging them into the freeway.

The curveball: she is an original character instead of a name pulled from the comics. Marvel does this more than people realize, especially during the Multiverse Saga, where they keep the chessboard flexible. That usually means a smaller, contained introduction with room to scale up later if the story asks for it.

The fan-favorite theory: Jean Grey. As noted by Forbes, Sink's age, profile, and timing line up neatly with Marvel inching toward a Mutant era. It is clean on paper, but nobody at Marvel has gone on the record about mutants here, and until they do, it is just smart speculation.

Why Marvel is rolling out new faces this way

The MCU is not in the Phase 1 playbook anymore. Lately, Marvel introduces characters without immediately defining how big or how fast they will matter. Look at Shang-Chi, Yelena Belova, and America Chavez: each started in a tidy story, then got positioned for bigger crossover energy later. Same deal with a bunch of Disney+ characters, where the studio has taken its time deciding when they reappear.

That slow-burn approach fits the Multiverse Saga, where the studio is still stitching pieces together. Bring a character in, see how audiences react, then decide how far to push the throttle. By that logic, Sink showing up in Brand New Day could be step one rather than a one-and-done.

The bottom line

Sink's casting is both the answer and the question. She is in the movie. We do not know who she is. The buzz says it might be bigger than a cameo, and there is smoke around Secret Wars, but nothing official connects those dots yet. For now, expect Marvel to keep this one in the vault until they feel like dropping the reveal.

Got a theory for who she is playing? Drop it in the comments. If anyone nails it early, I will be impressed.