Only two Stranger Things colleagues knew about Jean Grey casting, says Spider-Man 4’s Sadie Sink
Marvel kept Sadie Sink’s Jean Grey casting in Spider-Man: Brand New Day under wraps, but two Stranger Things colleagues were in on it — and she’s said who.
When it comes to keeping casting secrets in the Marvel universe, you’d think the studio had a batphone straight to MI5. Case in point: Sadie Sink, now publicly Jean Grey in Spider-Man: Brand New Day, kept her involvement as quiet as humanly possible — except for a select few who got the heads-up before anyone else, apparently thanks to a bit of professional trust and, well, the reality of working on another massive Netflix project at the same time.
Spider-Man: Brand New Day is 2026’s top-grossing film, smashing past $1 billion worldwide.
Who Was in the Know
As it turns out, Sink did confide in her immediate circle — her family, of course, but also the twin brains behind Stranger Things, Matt and Ross Duffer. In a recent Variety interview, she got a bit honest about the maths:
When pressed by Variety, Sink admitted, 'I mean, it was definitely more than three, if I’m being honest. You have people that you can trust within the industry to talk about it.'
The reason the Duffers made that inner circle is fairly straightforward — at the time she landed the Jean Grey gig, she was busy filming another season of Stranger Things. It seems a bit unrealistic to ghost your directors when a life-changing Marvel role drops in your lap. Sink broke the news to them early, and, unsurprisingly, the pair were absolutely thrilled for her.
She explained to Variety that the Duffer brothers have been massive supporters throughout her career, having watched her grow up on their set. Their reaction apparently was instant enthusiasm, telling her that Jean Grey 'is the best character', insisting she 'had to do it', and reassuring her she was perfect for the role and would be 'amazing'. Considering the Duffers’ knack for genre fandom and their solid comic book knowledge, Sink said it was a big deal to have their stamp of approval before the Marvel media circus even kicked off.
Marvel’s Tight Ship, Smashed Records
Marvel, as usual, had all hands on deck to prevent leaks ahead of the Spider-Man: Brand New Day premiere, even by their ferociously tight standards. Despite the internal secrecy, a few trusted insiders did get wind of the casting, though Sink swears the list really was a small one. None of it seems to have hurt the film’s box office run, either. Brand New Day continues to dominate worldwide, sitting comfortably atop the 2026 charts after clearing the $1 billion barrier — not a bad haul for a film that the main cast evidently had to keep under wraps even amongst friends.