If there is still one aspect of the upcoming Spider-Man: Brand New Day that still comes across as the most mysteriously intriguing while at the same time void of actual details, it’s Sadie Sink’s mystery character.
As of right now, the most prominent theory that has been circulating the internet about the Stranger Things actress’s character is that she is actually mutant Jean Grey from the X-Men franchise in disguise. A new Chinese promo has appeared online giving us the first real information of who Sink may be playing, but even with this new info there are still a lot of questions due to the intentionally vague nature of the description. According to the Chinese entertainment website, Sink’s first official character description goes as follows: “A mysterious figure, whose true identity remains unknown, is also lurking in the shadows: whether friend or foe is still unclear.”
The character most think Sink is playing in mutant Jean Grey, one of the most powerful mutants in Marvel’s lore and one of the most prominent characters in the Fox/X-Men timeline with both X3 and Dark Phoenix films focusing on her transformation into an ultra powerful alter-ego, Phoenix. Phoenix is a legendary cosmic entity that is constantly reborn, and emits a Phoenix Force that merges with Jean Grey to create the evil alter-ego. Other less probably theories include Sink playing Black Cat, Gwen Stacy, or even the theoretical daughter of Tobey Maguire’s Peter Parker, Mayday Parker. Many believe that Sink is playing Jean Grey due to early plot rumors and the fact Marvel is being extremely secretive over the character, and with the MCU on the verge of a full scale mutant renaissance the timing lines up perfectly. Back in December and January, early plot leaks claimed that her character would be on the run from the Department of Damage Control, which is also thought to have a large presence in this film. Not many other details are known but you can actually read all the claims that first surfaced in December when we did a story on it back on December 23rd of 2025.
It’s also been heavily theorized that The Punisher’s role in the film will be in pursuing Sadie Sink’s character on behalf of the Department of Damage Control. It’s been known for a long time that Jon Bernthal’s Frank Castle will have a major presence in the upcoming Spider-Man film, which at first glance seems like a strange addition to the historically more kid friendly franchise, but Marvel and Sony seem to be going for a darker tone this time around. While The Punisher lends itself to a more adult-themed storyline, at the end of the day Spider-Man is still (and most likely always will be) a franchise that caters to a younger audience so using Punisher as a pursuant for the potential Jean Grey is a great way to utilize his character without having to go to ultra-violent route of The Punisher Netflix series. It’s thought that Peter Parker will be tasked with protecting her character from both the Punisher and the DODC, but that will remain to be seen when the film releases.
It’s been known for quite a while that Marvel is going full swing on the X-Men in the coming years with their first major MCU appearance (if we’re not taking Deadpool and Wolverine too seriously) in Doomsday coming out later this year in December, and is actually the next movie in the Marvel lineup releasing after Brand New Day. One of the main reasons I think a lot of this particular Spider-Man movie is being kept under such heavy wraps is because it will have a large emphasis on mutants and Marvel does not want to spoil their versions of the infamous characters in a strategy that will help differentiate their versions of the characters from the versions we all have watched in films for the part 20+ years from Fox. Adding an air of mystery to the character helps to enhance the anticipation for both the Spider-Man film and the next phase of Marvel films that will presumably focus on the X-Men.
For now, everything regarding her character is strictly speculation and will most likely remain that way until the film comes out on July 31st. Marvel’s marketing is clearly much different for this Spider-Man film this time around, which signals something big or different happening in this chapter. Even the first character synopsis is vague, which I am honestly thankful for because it’s been quite a while since I’ve walked out of a Marvel film feeling genuinely surprised with the plot. If there is one thing the MCU is not known for, it’s keeping details of their films quiet, so if this film somehow is able to while also leading into Doomsday then dare I say did Marvel finally figure that aspect of their marketing out? As of right now, we can only guess. Who do you think Sadie Sink’s mysterious character is? Let us know your theories and guesses in our comments or our Instagram and make sure to check out the Chinese page if you want to translate the character description for yourself, which you can do right here. (Keep in the mind the page is in full Chinese).
