This story contains huge spoilers from episode five of WandaVision.
Every single episode of WandaVision has been a rollercoaster, but the most recent installment of the twisty Disney+ series quite literally changed the Marvel Cinematic Universe with just one cameo from a character who is not exactly canon: Quicksilver.
In episode five, the cracks are finally beginning to show in Wanda's (Elizabeth Olsen) picture-perfect life with Vision (Paul Bettany) in Westview. From the outside looking in, S.W.O.R.D. and the FBI have discovered that Wanda is holding the residents of the small town hostage in what they call "The Hex," controlling their movements and keeping them from unlocking their consciousness. Within The Hex, Vision is starting to make his own realizations; Wanda's odd behavior and a frenzied conversation with his co-worker leads the synthezoid to the same discovery, threatening the harmony of his and Wanda's family home.
At the same time, however, it feels like maybe Wanda isn't in complete control of everything going on in Westview. Her twins Billy and Tommy are able to age up at will, things from the outside world can still enter her warped reality (like, Monica Rambeau and the litany of S.W.O.R.D. drones sent in), and her brother is actually alive. Kind of.
We first met the Maximoff twins in the 2015 film Avengers: Age of Ultron. As children, their parents were killed when a bomb — made by Stark Industries — blasted their apartment building to pieces. Orphaned and grieving, Wanda and Pietro (played by Aaron Taylor Johnson) fueled their angst into a revenge plot against Tony Stark (Robert Downey Jr.) and the Avengers. They volunteered to be part of a HYDRA experiment that gave them superpowers, and when Ultron (James Spader) approached them to help take down the superhero squad, the siblings happily joins forces with the killer A.I.
But the Maximoffs' allyship with Ultron didn't last long; when they discovered that Ultron's ultimate goal was to wipe out mankind, they quickly switched sides and began working with the Avengers. The fight that ensued was especially devastating, destroying their hometown of Sekovia and resulting in Pietro's death.
Fast forward to now, with Wanda's grief over her many personal losses powering a whole new altered reality in Westview. In the middle of a particularly intense fight with Vision, the doorbell rings, and it's Pietro. But not the Pietro MCU fans know. This Pietro/Quicksilver, back from the dead, is the version from Fox's recent X-Men films (Days of Future Past, Apocalypse, Dark Phoenix) played by Evan Peters. It looks like Wanda just... recast her own brother.
What does this mean for WandaVision? It's hard to say exactly, But everything in this show happens for a reason. Peters' sudden appearance in WandaVision could actually open up a new world of possibilities in the MCU. (Plus, it's giving American Horror Story fans a new reason to tune into the show.)
For years, Professor X (played by Patrick Stewart and James McAvoy) and his team of powerful mutants have been kept outside of the MCU despite Avengers and X-Men crossovers occurring frequently within Marvel Comics simply because their storylines were property of 20th Century Fox. With its 2017 billion dollar acquisition of the company, Disney now has full ownership over many of those characters and their films, meaning that there is a future in which mutants like Storm, Wolverine, and others interact with our MCU faves. This might actually be the first move towards officially welcoming mutants into the MCU fold.
True to WandaVision's wild plot, nothing is for certain — we'll just have to wait until next week to find out why any of this is happening.