Singer Steve Lacy appears to have inadvertently revealed a major plot point of "Spider-Man: Brand New Day" during a livestreamed red carpet interview at the film's premiere. Asked which character he was most excited to see, Lacy named "Jean", widely taken as a reference to Jean Grey of the X-Men, seemingly confirming that Sadie Sink's previously unnamed mysterious villain character in the film is Jean Grey. The apparent slip matters because it undercuts efforts to keep the character's identity secret through the marketing campaign and confirms long-running fan speculation about the X-Men's introduction to the Marvel Cinematic Universe.

Lacy, whose track "Oh Yeah?" features on the film's soundtrack, made the comment when asked to name his favourite character without spoiling anything, saying: "You know what? Jean. I like Jean. She's the villain but there's a reason to her madness." The X-Men characters became available to Marvel only after Disney's 2019 acquisition of 20th Century Fox, and Sink's role in Tom Holland's fourth Spider-Man film had been kept deliberately mysterious. The comment prompted confusion and frustration among fans online, even as early critic reactions to the film, which several called "awe-inspiring", have been positive ahead of its release.