We were tricked into thinking that he was an inter-dimensional traveler, but it turns out that some of the things Mysterio said about the multiverse were not really that inaccurate.
The concept of the multiverse was officially introduced in 'Spider-Man: No Way Home' and 'Loki', but Tom Holland's Peter Parker encountered what could have been a multiverse teaser in his second movie, 'Far From Home'.
We all remember Mysterio – a self-described inter-dimensional traveler who turned out to have lied about his origin being another universe. Still, Jake Gyllenhaal's character did mention that he arrived to the universe dubbed… 616. Which ended up being actually true, as revealed in 'Doctor Strange in the Multiverse of Madness'.
The writer behind the Doctor Strange sequel, Michael Waldron, seems to be curious about that as well.
"I guess it begs the question, what did Quentin know? He was a smart guy. Um, is it just a coincidence? That's… I don't know," he admitted in an interview with Rolling Stone.
Of course, Mysterio could have found that out via a multiversal dream – and Waldron seems to be okay with that theory – but some fans suggested that it might as well have been a plothole.
Or an Easter egg that did not age well.
Waldron's logic that we experience the lives of our variants when dreaming kind of makes Mysterio's wild guess explainable. Besides, Mysterio was not the first character in MCU to dub "our" universe 616 – it was also done by Dr. Selvig in 'Thor: The Dark World'.