Marvel fans are convinced Aubrey Plaza's Agatha All Along character is the child of a fan-favorite villain

Warning! This article contains spoilers for Agatha All Along episodes 1 and 2. If you've yet to tune in, and don't want to know anything that happens, turn back now!

Ahead of Agatha All Along's premiere, Aubrey Plaza practically confirmed that her character Rio Vidal, who doesn't appear in the Marvel Comics, is going to be revealed as someone else later down the line. Now, having seen episodes 1 and 2, viewers are convinced they know who...

Towards the end of the WandaVision spin-off's opener, Rio attacks Agatha (Kathryn Hahn) at her home in Westview, but the latter wiggles her way out of the brawl by persuading Rio to wait and fight her when she's regained her powers – and is therefore a worthier opponent. 

"Don't you want me at my best? Let me get my purple back, and then come find me," Agatha purrs. "After all these centuries, Agatha Harkness will finally meet her end. Oh, it really warms the heart," says Rio.

"You don't have a heart," Agatha scoffs, as Rio snaps back: "Yes, I do. It's black, and it beats for you."

In episode 2, as Agatha and Teen (Joe Locke) pay a visit to clairvoyant witch Lilia Calderu (Patti LuPone), who predicts that she, Jennifer Kale (Sasheer Zamata), Alice Wu (Ali Ahn) will make up Agatha's coven. There's one more person on the list, though, but she can't quite "see" their name and finds herself drawing a black heart. Agatha's reaction to it suggests she knows who it is, and she's not happy about it...

As readers have pointed out on Reddit and Twitter, Blackheart is the son of demon-lord Mephisto, a big bad that was fans were desperate to see introduced in WandaVision, in the comics. 

"Okay, so she's 100% playing Blackheart, right? And fans will "go crazy" because they're the child of Mephisto, right?" one Twitter user claimed, as another wrote: "I'm calling it now, She's a gender-swapped Blackheart, daughter of Mephisto."

Others, however, think Rio will actually turn out to be human-fairy hybrid Morgan Le Fay, while a few more think she could be Doctor Strange character Gaea or an interpretation of Dian, the Emerald Warlock and Agatha's Department of the Uncanny teammate.

"I'm just so happy they let me play this character," Plaza previously told Scarlet Witch Updates. "I can't spoil it, but what happens, the reveal is pretty amazing. And I think for the fans especially, they're going to go crazy." 

Agatha All Along episodes 1 and 2 are streaming now. Ensure you don't miss a thing with our Agatha All Along release schedule. 

For more on the wider MCU, check out our guide to all of the upcoming Marvel movies and shows or get up to speed with our breakdown of the Marvel timeline.