Updated: February 22, 2021
Disney+ has finally kicked off the MCU's Phase 4 with WandaVision, a 50s-styled, sitcom-based television show set in the idyllic town of Westview. Played by Kathryn Hahn, Agnes is the peppy know-it-all on the block, but her name and costume accessories suggest she's a significant character in Scarlet Witch's comic-book arc. Agnes was first introduced as Wanda and Vision's nosy neighbor. WandaVision didn't explain who she was outright, but there were several clues that suggested there was something fishy going on with her — namely, she often referenced a husband, Ralph, who never appeared, and she was the one Westview citizen Monica Rambeau, Jimmy Woo, and Darcy Lewis couldn't identify. Fans speculated for a long time that Agnes may be linked to comic-book villain Agatha Harkness.
In Marvel Comics, little is known about Agatha Harkness' origins. She's a witch who has been around long enough to see the fall of Atlantis and has since joined the New Salem community, battled the Frightful Four, teamed up with the Fantastic Four, and provided guidance and training to Scarlet Witch. After she is burned at the stake by her grandchildren, also known as the Salem's Seven, she is resurrected by mysterious means and tells Scarlet Witch that her children with Vision are actually remnants of Mephisto, Marvel's Devil. Agatha wipes Scarlet Witch's memories of her children, which causes her to lose her mind and eventually kill Agatha again.
Eagle-eyed viewers first noticed Agnes wears the same brooch as her comics counterpart in the beginning episodes and later donned a witch's hat as part of her Halloween costume. In the comics, Agatha Harkness is often portrayed with a brooch near her neck as well. Agatha does influence Wanda in the comics, so it makes sense that Agnes is making a worthy effort to be a part of Wanda and Vision's life. As soon as she's introduced to the show, she offers Wanda support in planning a romantic anniversary dinner for Vision, lends Wanda pots and pans when she needs them, and gives her the rundown of the community fundraiser meeting. After seven episodes, Agnes was finally revealed as Agatha Harkness in a musical rendition called "Agatha All Along," which confirmed that the wily witch was behind every strange occurrence in Westview, including the arrival of Pietro.
Agnes is also more personable and fun, taking the time to get to know Wanda almost to an uncomfortable degree. However, while Agnes has been revealed as Agatha, there is still much to learn about her motivations for Westview and Wanda. During the seventh episode of WandaVision, called "Breaking the Fourth Wall," Agnes asks Wanda if she ever thought she deserved what was happening to her. But, why does Agnes feel Wanda deserves being trapped in Westview with her dead husband? What is Agnes getting out of all of this and is she working with someone on the outside? Perhaps by creating this magical façade, Agnes is getting a better picture of Wanda so that she may train her to better utilize her powers. Conversely, Agnes could be using Wanda to obtain something far greater in the outside world. Maybe she's even working with Director Hayward, who was recently confirmed to have been trying to bring Vision back online. There is still a lot the audience doesn't know, but the reveal of Agnes as Agatha Harkness certainly paints a bit of a clearer picture regarding who is the true mastermind behind Westview. Now all fans need to know is the why of it all.
Whether Agnes will wield her full powers and be revealed to be working alongside another villain in WandaVision remains to be seen. Wanda and Vision are no longer being monitored by S.W.O.R.D., and it's not outside the realm of possibility to believe that Agnes has control over other alternate realities standing in as TV series. Hopefully, more information will be provided about Agnes and her devilish plans in the final two episodes of the series.