There are only a few days left until Spider-Man: Brand New Day finally swings onto the big screen. But that has not stopped fans from speculating about what lies ahead for Peter Parker in his fourth standalone adventure, where the world no longer remembers who he is. From Jean Grey to Matt Murdock, there are countless theories about the film's story and surprise appearances. 

And one of the most intriguing theories involves the Hulk, more specifically, a special Grey Hulk form that has yet to make its live-action debut. 

The first trailer for Spider-Man: Brand New Day gave fans a glimpse of brilliant scientist Dr. Bruce Banner living a quiet life, while also teasing his Hulk form. However, content creator Daniel Grinspan suggested an intriguing theory on social media, suggesting that the Hulk seen in the trailer may not be the familiar Green Hulk at all. It could actually be the long-awaited Grey Hulk!

He pointed out that Marvel was previously rumored to have removed and hidden things or characters from their trailer to avoid spoilers. Grinspan connected this idea to another popular fan theory claiming that Jean Grey could appear in the film and use her psychic abilities to manipulate Banner. As per the theory, instead of releasing the Green Hulk, Jean Grey's influence could give rise to the Grey Hulk, a more cunning and calculating version of the character. 

He also pointed to Avengers: Endgame, where Banner merged his intellect with the Hulk to become Smart Hulk. In the Spider-Man: Brand New Day trailer, however, Banner appears to be wearing an inhibitor. Grinspan questioned why such a device would be necessary if Banner already had complete control over his Hulk transformation, arguing that it could hint at the emergence of a different Hulk personality.

Now, Grey Hulk has never appeared in live-action, despite being the character's original intended color. When Hulk first debuted in The Incredible Hulk #1 in May 1962, he was grey, but ink inconsistencies led the character to be changed to green. If Grinspan's theory is right, Grey Hulk could finally appear on screen for the first time.

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Much like the Jean Grey speculation, there is also a popular theory surrounding Matt Murdock's potential role in Spider-Man: Brand New Day. 

Matt Murdock has long been rumored to make an appearance alongside Spider-Man in Spider-Man: Brand New Day. During an interview on Jimmy Kimmel Live!, Charlie Cox was asked whether he would be appearing in the film. While the actor denied the rumors, he also admitted that he would have given the same answer even if he were part of the movie, doing little to put the speculation to rest.

"No. But if I was in the movie, I would also say no. BUT... I'm not in the movie," he said.

Now, there are clues too. One of the biggest clues fueling theories about Daredevil's return is the presence of the Hand in the trailer. The infamous ninja organization has deep ties to Daredevil's past, making Matt Murdock's involvement seem plausible if the group does play a major role in the story. However, the film's plot is tightly under wraps, leaving fans to speculate until Spider-Man: Brand New Day arrives in theaters on July 31, 2026.

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What do you think about this new theory about Spider-Man: Brand New Day? Let us know in the comments.