Patrick Stewart's Professor X is arriving in Doctor Strange in the Multiverse of Madness, but a theory claims the X-Men were always secretly in the Marvel Cinematic Universe. The Doctor Strange 2 trailer had a shocking reveal with Professor X and the X-Men. In the trailer, Doctor Strange (Benedict Cumberbatch) deals with Scarlet Witch (Elizabeth Olsen) messing with the Multiverse, he fights across dimensions alongside America Chavez (Xochitl Gomez), and he even goes to trial over apparent Multiversal crimes. However, during Stephen Strange's trial, a "Mystery Voice" says, "We should tell him the truth." This voice apparently belongs to Patrick Stewart's Professor X, so the moment puts the X-Men in the MCU.
Marvel's Patrick Stewart moment has been a long time coming. The studio finished purchasing Fox entertainment assets in 2019, giving Marvel the right to use the X-Men and the Fantastic Four. However, the X-Men haven't entered the MCU thus far. WandaVision teased the arrival of the X-Men with Evan Peters' Pietro Maximoff/Quicksilver. However, that turned out to be a trick. The Disney+ series reveals Peters' character was just a brainwashed civilian named Ralph Bohner.
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Though the Doctor Strange 2 trailer seemingly brought the X-Men to the MCU, they may have been secretly around the entire time. According to a theory (via Reddit), the X-Men were always in the MCU, but Professor X previously mind-wiped the world using Cerebro before the events of 2008's Iron Man. The theory states that there was a significant conflict between humans and mutants, and it ended with a pact to erase humankind's knowledge of the X-Men. Because of this pact, Magneto
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