[Editor's note: The following contains spoilers for WandaVision, Season 1, Episode 5, "On a Very Special Episode..."]

Among the many meta-textual and casually terrifying mind-ruptures going on in WandaVision, Episode 5 ends with a bang. Wanda's (Elizabeth Olsen) dead brother Pietro comes back, seemingly sprung out of Wanda's increasingly oppressive sitcom imagination. But it's not the MCU version of Pietro, aka Quicksilver, played by Aaron Taylor-Johnson that shows up at her door. It's the formerly Fox-owned now Disney-owned X-Men version of Pietro, played by Evan Peters. A "recast," as Darcy (Kat Dennings) puts it. How in the heck did they pull this bold move off?

WandaVision showrunner Jac Schaeffer spoke with Marvel.com (synergy!) about this storytelling move, admitting from the jump that while they "loved the idea of" resurrecting Quicksilver, they were unsure how that could play out justifiably. "We were like, how in the world are we going to make this make logical sense? Like, how do we justify this? Because that's the thing, you can hatch a million great ideas, but to make them land, to make them be grounded, to make them feel organic to the larger story." Schaeffer also explained that Kevin Feige "wanted to make sure that there was a reason for it, that it made sense. And I hope that's what we did."

Logistical hurdles aside, Schaeffer knew she wanted to make this move, and that it would feel particularly of the show's spirit to use Peters in the role.

"This show is such a mind scramble, and because it's working on so many levels, and there's so many notions of what's real and what's not, and performance, and casting, and audience, and fandom, and all of that, we just thought it would be the biggest thrill to bring Evan over to the Marvel Cinematic Universe."

So how did they craft their in? Like many other moments from the show, it all stemmed from the sitcom trope. As Schaeffer explained, "We thought like, how do we give him this entrance, and then enjoy that, and then make it crazy? And we had long had the idea of the trope of the brother, or the relative, or whoever comes to town and like, stirs things up with the family — that sitcom trope."

"We were rooting for it for so long, and didn't know if it would be possible," continued Schaeffer. "It was complicated to make happen. Evan was always up for it — like, always, always, always. He is a comic book fan, and a Marvel fan. He is always up for the absolute weirdest option. And he's a pleasure — truly a pleasure to work with." This is great news to hear, and could set quite the multiverse-collapsing precedent for the MCU moving forward — especially given this Spider-Man 3 news.

For more from Schaeffer about WandaVision, here's our exclusive interview with her.