Sadie Sink has spoken to Collider about her closely guarded role in Spider-Man: Brand New Day, the upcoming Marvel film in which she makes her secretive on-screen debut. The Stranger Things star said the secrecy surrounding her character surpasses even the tight-lipped production of Stranger Things' final season, reflecting the intense fan speculation that has surrounded her casting since the first trailer was released. Her involvement matters because it has fuelled widespread theories about which character she might be playing, with the answer likely to have knock-on implications for the wider Marvel Cinematic Universe.

Speaking to Collider's Steven Weintraub ahead of the film's 31 July release, Sink discussed comparisons between the confidentiality demanded on Brand New Day and her four seasons on Stranger Things, when she played Max Mayfield, admitting the Marvel secrecy is "even more intense." Fan theories about her character range from X-Men figure Jean Grey to Spider-Girl, Firestar and Gwen Stacy. The film follows Peter Parker (Tom Holland) grappling with the aftermath of Spider-Man: No Way Home, alongside co-stars Jon Bernthal as the Punisher and Mark Ruffalo as the Hulk, with direction from Destin Daniel Cretton.