Tucked away in Doctor Strange in the Multiverse of Madness was a throwaway line that both infuriated and confused long-time fans. When Strange journeyed to Earth-838, he was told that his reality, the familiar MCU Earth, is known as Earth-616. This number will be very familiar to comics readers, as it’s also the designation of the core comics’ universe.
That set the cat among the pigeons as up until now the MCU had been designated Earth-199999 in secondary materials, putting in the same cosmology as the comics. But there’s another wrinkle in the story that’s resulted in an interesting fan theory.
In the MCU our first real mention of the multiverse came via Mysterio in Spider-Man: Far From Home, who was introduced saying: “There are multiple realities, Peter. This is Earth Dimension 616. I’m from Earth 823.” Mysterio’s cover story was a lie, so how did he know the correct multiversal designation of MCU Earth?
It’s possible that this is simply a coincidence, though it can be worked into continuity in a neat way. You see, Mysterio didn’t write his backstory, fellow former Stark Industries’ employee Guberman did. So, how did Guberman know about Earth-616? Could he have been involved in secret multiversal research going on right under Tony Stark’s nose? After all, the company was trying to push the boundaries of what was possible with science…
It’s here that the theory gets a little hazier, as it’s posited that Guberman made contact with Earth-838 and nobody believed him, so he decided to get the truth out there via Mysterio (who just accidentally said “828” rather than “823”). However, Thor: The Dark World showed Erik Selvig scrawling “616 universe” on a blackboard after recovering from Loki’s mind control in The Avengers, so perhaps “616” is just a fringe science theory in the MCU.
Or maybe Marvel Studios just didn’t think this far ahead and didn’t realize the can of worms Christine Palmer’s line would open up. You be the judge.