The first two episodes of WandaVision dropped last Friday, and they've already prompted A LOT of fan theories amongst the Marvel faithful. There is one that is gaining particular traction though, mainly because it would have far-reaching implications for the rest of the MCU, but also because there may actually be a lot of weight to it.
The theory stems from the second episode, when Agnes (Kathryn Hahn) introduces Wanda (Elizabeth Olsen) to Dottie, the proverbial Cul-de-Sac Queen who's at the centre of Westview's social circle. Dottie mentions that "the devil is in the details" while discussing things with the local committee, before Agnes interjects and says "that's not all he's in."
While this could be more patented snark from Hahn's character, some have taken this as a tacit indication that the figure pulling the strings behind the scenes, and keeping Wanda trapped in this classic slice of Americana, could in fact be Marvel's own version of the devil - Mephisto.
Mephisto, for those who don't know, is one of the most powerful villains in the Marvel Universe - and he has a history with Wanda Maximoff. More commonly associated with Ghost Rider than any other Marvel hero, being the man responsible for Johnny Blaze becoming the Spirit of Vengeance, the character rules over Hell and has had run-ins with Thanos, Doctor Strange and Spider-Man (although Spidey fans would probably want you to forget that last part).
He's the ideal candidate to take a leading role in MCU Phase 4, with WandaVision only just the beginning...