When Evan Peters first popped up in episode five of WandaVision as Wanda's late brother Pietro, there were a lot of fan theories about his true identity. While some assumed that the MCU was finally crossing over to the X-Men universe — since Peters played Pietro in the X-Men movies — or that his character would turn out to be Marvel comics villain Mephisto, all of those theories ended up being dead wrong. Turns out, he was simply just another regular resident of Westview.
In the season finale, Monica is held captive by fake Pietro as an epic showdown between Wanda, Vision, White Vision, and Agatha Harkness goes on outside. While fake Pietro is able to push Monica back with one simple touch, she later learns that he doesn't actually have any magical abilities. Instead, he is being controlled by Agatha Harkness with a beaded necklace.
After finding his mail and a headshot, Monica eventually learns that his true identity is an actor named Ralph Bohner. Before you go searching that name to find the hidden significance, no, Ralph isn't some special Marvel comics character or a hidden Easter egg. He's really just a regular guy who found himself trapped inside Wanda's Hex.
Funnily enough, the house that Agatha Harkness/Agnes has been living in this whole time is actually Ralph Bohner's. Remember the "husband Ralph" that Agnes kept referring to in earlier episodes? It's actually been Ralph Bohner all along! Well played, Marvel.