The original plan for Spider-Man: No Way Home's multiverse was very different, and the movie would have been much worse if the MCU had kept that direction. In No Way Home, Spider-Man's secret identity was outed by Mysterio, and he had to deal with the fallout of the event. During the time when people knew Spider-Man was Peter Parker, those closest to him were put in harm's way, so he decided to go to Doctor Strange to cast a spell on the world for everyone to forget that Peter Parker was Spider-Man.
When Doctor Strange attempted the spell, Peter interrupted him, and the spell went out of control, bringing in Spider-Man villains from other universes. He eventually beat the five villains that came into Earth-616 with the help of other versions of Spider-Man, but none of this was originally meant to happen. In a recent interview, writers Chris McKenna and Erik Sommers discussed alternate storylines that almost made it into the movie, and some that almost didn't occur, including No Way Home's original multiverse plan.
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Spider-Man: No Way Home almost didn't involve the multiverse as a central focus and was only planning to introduce and tease the multiverse at the end of the movie. The multiverse stood in the center of the film, making the plot, storyline, and the best scenes impossible to have been performed without having the multiverse as part of the film. When the Reptile, Electro, Doctor Octopus, Sandman, and the Green Goblin crossed over into Earth-616, it was met with great reviews. The kind of excitement people had for the multiversal moves in the film was unprecedented. The moment when Tobey Maguire and Andrew Garfield came through Ned's sling ring
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