One of the biggest surprises in Marvel's WandaVision was the arrival of Pietro Maximoff in the fifth episode, "On a Very Special Episode..." played not by Aaron Taylor-Johnson as the character was in Avengers: Age of Ultron, but by Evan Peters, the actor who brought Quicksilver to life in the X-Men movies. It's since been revealed that this "Pietro" may not be the real deal -- last week's episode revealed that Agnes (Kathryn Hahn) is really Agatha Harkness and has been pulling strings all along -- and it turns out that it's part of the reason the series went with Peters rather than Taylor-Johnson.