One of the biggest surprises in the Disney+ Marvel show WandaVision was the appearance of Evan Peters as Wanda's brother Pietro. Showrunner Jac Schaeffer has spoken more about this, and revealed there was no back-up plan if Peters couldn't do it.

Peters played Pietro--aka Quicksilver--in the X-Men films, with Aaron Taylor-Johnson appearing as Pietro in the Marvel Cinematic Universe. While the movie rights to the X-Men are now owned by Disney, the two superhero universes are yet to cross. The final episode of WandaVision reveals that it's not Pietro at all, but an ordinary man named Ralph Bohner that Wanda has "recast" as her dead brother, making Peters' appearance little more than an in-joke. Nevertheless, Schaeffer states that she was only given permission to use Peters at the last minute.

"[Using Peters] was an enormous question mark for a very long time," she told the New York Times. "And it took a while to figure out if it would be possible. It was late that it was finally confirmed that we could do it. But we were writing for it. Evan is such a chameleon in that way, that could play an amalgamation of [Full House']s Uncle Jesse, [Family Ties'] Nick, and Joey from Friends. He could play those layers."