Sadie Sink enters the Marvel Cinematic Universe on July 31 without an audition, a character name, or a single frame of promotional footage. Director Destin Daniel Cretton offered her the part directly, drawing on their prior collaboration on The Glass Castle in 2017. She did not receive a script until she arrived in London to begin filming.
Her role remains entirely undisclosed. Marvel Studios has excluded Sink from all trailers and marketing for Spider-Man: Brand New Day, which also stars Tom Holland, Zendaya, Jacob Batalon, Mark Ruffalo, and Jon Bernthal. Fan speculation has centered on young Jean Grey, tied to Marvel's longer-term plans to introduce a younger generation of X-Men into the MCU, though Sink has confirmed nothing.
Speaking in recent press interviews, Sink described entering an established franchise as its only unknown quantity. "It was interesting stepping into that space and being a little bit of an outsider in that way, but he could not have been more welcoming," she said of Holland. Asked about protecting Marvel secrets, Sink pointed to nine years keeping Stranger Things spoilers under wraps. "You just don't share the secret," she said. "It's not that hard."
Spider-Man: Brand New Day opens in theaters July 31, 2026.
