Why Spider-Man Was Mutating in Brand New Day, & How His New Powers Compare to His Old Ones
Spider-Man: Brand New Day changed Spider-Man in many ways, and it all came down to his body and powers mutating in strange ways. When the movie started, it had been a few years since Doctor Strange cast his spell that removed Peter Parker from everyone’s memories, and he went on to become one of New York City’s most beloved and respected heroes. He had beaten almost every supervillain who came along and gained the respect of the police and the Department of Damage Control (DODC). However, he was also completely alone, and that isolation is what set off the changes in his DNA mutating in unexpected ways.
In the movie, Spider-Man ended up with some new powers, some upgrades to his old powers, and it was all because of the decisions he made in Spider-Man: No Way Home.
The Reason Spider-Man Was Mutating in Brand New Day

Spider-Man had shown from the start of the movie that there was something wrong. He kept feeling something was wrong with his wrists. He was also having bad headaches, something he had even told his police detective friend Jean DeWolff about. That led to a devastating moment after he saw Ned Leeds, followed him to a house party, saw MJ, and realized she had a new boyfriend. He went home and collapsed. When he woke up, he was stuck in webbing on the roof’s ledge and realized something major had happened to his body. This all culminated in him realizing his body was producing organic webbing he could shoot from his wrists.
Spider-Man learned from his AI Assistant E.V. (voiced by Naomi Watts) why he was mutating. According to E.V., his body was reacting to a mix of trauma and emotional distress, and Peter realized quickly that this was based on him seeing Ned and MJ again, and realizing how alone he was. E.V. also pointed out that Peter was isolated and alone, and the longer he was by himself and cut off from everyone else, the more he would lose what made him human. He was losing his identity as Peter Parker and becoming more spider by the day. There was even a spider documentary shown on the computer monitor in his apartment (narrated by Keith David) that showed how spiders transform over the years.
In Marvel Comics, a similar event happened after Spider-Man fought Morlun, had his eye ripped out, and then seemingly died in the hospital. He woke up encased in webbing (similar to Peter in Spider-Man: Brand New Day), and then he realized his body had healed itself and he had new powers. In the comics, he received night vision, venomous forearm stingers, and more. The new powers in the movie were not on that level, but they were a big enough power-up to make Spider-Man the strongest he has ever been on the big screen.
Spider-Man Has New Powers After Brand New Day

The first new power that Spider-Man discovered he had was organic webbing, which shot out of his wrists. It was very weird, since his web-shooters wouldn’t work at all anymore. They glitched out because his body was now producing webbing of its own. It also meant that Spider-Man no longer needed to calibrate his web-shooters to work on the right levels, but he did have to figure out how to use his organic web-shooters (like Peter #2 as he called Tobey Maguire’s character in the movie). The movie went into painstaking detail to show how he used memory response to time his web-shooting to perfect it as he swung, although he took a beating the first few times he used them.
The second upgrade to his powers came with his spider-sense. What was originally the “Peter Tingle” that alerted him to danger was now more of a radar sense like Daredevil’s, and he could hear, see, and sense everything around him at an almost paralyzing level. He was almost crippled by the sensory overload. This is why he decided get Bruce Banner’s advice on making a power inhibitor to help him lower his powers to keep them more controlled. It wasn’t until he realized that he had to remove the inhibitor and just accept the new powers that he was able to control these new senses.
The last upgrade to his powers was the most significant. Spider-Man was always strong, and he was able to rip steel doors from their hinges and beat superhuman villains with just his baseline strength. However, in the final fight against the Hand at the Department of Damage Control facility where Jean Grey was being held, he ripped off the inhibitor and accepted the new powers. He was able to defeat the entire Hand and even overpower the DODC weapons made specifically to take him down. He even easily busted through a door that he was previously unable to budge.
Spider-Man: Brand New Day made Spider-Man stronger than ever, more agile than he has ever been, and with an enhanced spider-sense that let him take in everything around him. In the end, he reconnected with Ned Leeds, and it seems that this will allow him to keep his power upgrades, while also keeping his humanity. Spider-Man is the strongest he has ever been, and he has entered into the upper tier of MCU heroes based on pure strength.