Sadie Sink kept her Marvel role secret for more than a year. On the red carpet of the world premiere in Los Angeles, R&B singer Steve Lacy let it slip — her character in Spider-Man: Brand New Day is Jean Grey, the telepathic mutant who serves as a villain of sorts to Tom Holland's Spider-Man. Variety

The secrecy was elaborate. Sink's character was referred to by a code name on set for security. She told only a few trusted people the truth, including Matt and Ross Duffer, the creators of Stranger Things, the Netflix series that helped make her name. Variety

Sink is the third actress to play Jean Grey on the big screen, following Famke Janssen in Fox's original X-Men films and Sophie Turner in the 2010s reboot. She was offered the part after breakout performances in Stranger Things and The Whale, the 2022 Darren Aronofsky drama that earned Brendan Fraser an Academy Award. Variety

The film did not need the mystery to draw crowds. Spider-Man: Brand New Day, released in theatres on 31 July 2026, supplanted Avengers: Endgame as the biggest domestic debut in box office history, per Variety. It grossed $1.15 billion worldwide in its first seven days. Variety

For Marvel Studios, the casting is a chess move. Jean Grey is an Omega-level mutant — the highest power classification in Marvel's mutant hierarchy — and she is set to go on to star in Marvel Studios' upcoming X-Men film. Variety reported that Sink plays a young Jean Grey, positioning her as a bridge into a new, younger generation of X-Men characters entering the Marvel Cinematic Universe. Variety

How many Marvel films Sink is contracted for remains under wraps. She could not reveal the number when asked. Variety

Marvel Studios' own website lists Sink among the film's stars alongside Holland and Zendaya, confirming her place in the official billing. Marvel.com

For fans of the character, the arrival of a new Jean Grey carries its own weight. The role has been a central pillar of the X-Men franchise since the first film in 2000. Each actress has brought a different version to the screen, and Sink's take arrives inside a Spider-Man story rather than an X-Men one, a signal of how Marvel is folding mutant characters into its broader cinematic universe before giving them a film of their own.