Marvel fans had the shock of their lives after WandaVision episode five, when Wanda Maximoff opened her front door to find her dead brother Pietro alive and well. But it was not the Quicksilver she knew in life, played in Avengers: Age of Ultron by Aaron Taylor-Johnson. It was Evan Peters, who played the character in three X-Men movies prior to Disney’s acquisition of Fox.

Evan Peters and Elizabeth Olsen as Pietro and Wanda Maximoff on WandaVision.

Marvel Studios

Fans have all kinds of theories as to what that means. Is he really Pietro Maximoff from an alternate Earth within the Multiverse? That seems the most likely explanation. But a lot of people seem to think he’s Mephisto or the demon Nightmare in disguise, pulling the strings. That could be too. Of course, why Mephisto chooses to disguise himself as a version of Wanda’s brother’s she’s never met is a bit of a head-scratcher. But then, so is this entire series.

The recent Halloween episode of WandaVision seems to suggest that Evan Peters’ Pietro has the same memories of the MCU Pietro. This leads us to believe he might embody an old comic book trope—one that hasn’t found a live-action movie equivalent until now. The hero who crosses over from one universe into another, and whose history alters to appear as if they’ve always been there.

20th Century Studios/Marvel Studios

The concept of the Multiverse has been a mainstay of both Marvel and DC Comics for decades. Alternate versions of characters are sometimes so popular that they fold into the main Earth, home to the majority of the publisher’s comic book stories. Often, a character’s memories change once a crossover migration takes place. It seems likely that this is what happened to Pietro. He is the version of Quicksilver from the X-Men film’s Earth, but his arrival on the MCU Earth has altered his memories to reflect his new reality.

DC Comics

This is something we’ve seen happen in the comics over and over again. One of the first examples was prominent DC heroine Black Canary. The character was originally from Earth-2, where the Golden Age heroes of the 1940s resided. After Wonder Woman left the Justice League in 1969, she crossed universes to replace her. And the longer she was on this new Earth, her memories of the previous reality seemingly began to fade.

DC Comics

When DC Comics released their reality-altering crossover Crisis on Infinite Earths, dozens of characters from alternate worlds assimilated into DC’s main Earth. Power Girl had once been Superman’s cousin on Earth-2. Fury had been the daughter of the Earth-2 Wonder Woman. Blue Beetle had been one of the main heroes of Earth-4. Once absorbed into the main DC Earth, their memories changed to fit their new histories. Power Girl became an Atlantean princess. Fury was now the daughter of a different hero. Blue Beetle became a hero on the same world as the JLA.

DC Comics bought Jim Lee’s Wildstorm imprint in the late ’90s. After the purchase, characters like Grifter and the WildCATS remained in their own separate continuity. But when the Flashpoint event took place in 2011, it resulted in a new continuity of the New 52. After that, most of the Wildstorm characters became part of this new Earth’s history. It was as if they’d always coexisted with the likes of Superman and Wonder Woman.

Marvel Comics

Meanwhile, over at Marvel Comics, the 2015 Secret Wars limited series smashed up several different Multiverse Earths into one giant Battleworld. One of these was the Earth-1610, home of Marvel’s popular Ultimates comics line. That was where the Miles Morales version of Spider-Man was originally from. Once the old Multiverse restored, Miles crossed over into the “main” Marvel Earth, better known as Earth-616. And once he arrived, as far as anyone remembered, he had always been from their Earth.

Pietro Maximoff just may be the live-action example of this comic book trope. Assuming there’s manipulation going on by a nefarious entity like Mephisto or Nightmare, we still believe that his body really is that of the Peter Maximoff of the X-Men Earth. Otherwise, having Evan Peters play him seems more like stunt casting, which seems beneath Marvel Studios. Since the “old” Pietro Maximoff is gone, this new Pietro is simply taking over his “spot” in this universe. The truth could something completely different, of course. But right now, the breadcrumbs are leading us to the conclusion that this is the first crossover from one Earth to the next. Now, someone needs to tell Deadpool.