'Agatha All Along' Star Joe Locke Breaks Down That Big Billy Maximoff Episode

Warning: This story contains spoilers for Agatha All Along episode 6, “Familiar by Thy Side.”

Welcome to the Marvel Cinematic Universe, Billy Maximoff.

Since the premiere of Marvel Television’s Agatha All Along, one major mystery has loomed over the show: the identity of Teen, the goth high schooler played by Joe Locke. All season long, his true name has remained a mystery, obscured by a witchy sigil. But halfway through the series, Agatha Harkness (Kathryn Hahn) realizes the truth: Teen is actually the long-lost son of the Scarlet Witch.

Episode 6, titled “Familiar by Thy Side,” flashes back to deliver an emotional origin story. It reveals that Eastview teenager William Kaplan died in a car accident, shortly after celebrating his bar mitzvah. At the same time, the soul of Billy Maximoff — who ceased to exist after his mother dispelled the Westview Hex in WandaVision — comes to inhabit William’s body, living on as someone new.

Series creator Jac Schaeffer tells Marvel.com that she always wanted to have a Billy-centric episode, exploring how Billy/William endured and came to realize his magical inheritance.

“When we decided that we were going to bring Billy into the show, I wanted to give him his own episode in that way so we could stop, rewind, and understand this very complex journey,” Schaeffer explains. “Up until that point, he’s been painted as a familiar. He’s at times been infantilized and underestimated. So in order to feel that change, we needed to feel his whole story in episode 6.”

During the development process, Schaeffer and executive producer Mary Livanos frequently compared the episode to WandaVision episode 4, “We Interrupt This Program,” where the series flashes back to reveal that Teyonah Parris’ character Geraldine is actually S.W.O.R.D. agent Monica Rambeau. They wanted to structure Agatha episode 6 similarly, paying off foreshadowing from early episodes while also diving deep into Billy’s psyche.

“The show has a puzzle box nature to it, where every episode has something completely new to look forward to,” Schaeffer explains.  “It was fun to have another step-out episode in this show where we get to learn how Teen came to be a part of this coven and what questions he might have that he’s trying to answer by way of the Witches’ Road.”

To fully capture Billy’s complicated history, Schaeffer and Livanos knew they needed an actor who could handle all of the magical highs and lows. Early on, they recruited Heartstopper breakout star Locke, and Schaeffer remembers getting chills during his initial chemistry read with Hahn.

“We did a comedy scene, and they had great charisma,” Schaeffer recalls. “He was so charming. And then we did a dramatic scene, and it felt like the molecules in the room shifted. He’s a very animated, fidgety person, but when it’s time to act in a deep, dramatic moment, he goes still in a way where you’re pulled into him. It was like: That’s what we need for the son of the Scarlet Witch.”

Once Locke landed the role, he dove into research. (Billy, aka Wiccan, has a long history in Marvel comics and is a key member of the Young Avengers.) As a congratulations gift for landing the role, Livanos gifted Locke a copy of AVENGERS: THE CHILDREN’S CRUSADE (2010), one of Billy’s most iconic storylines, which Locke says helped inform his portrayal.

“I read all of that, whilst also having the ability and the freedom to make the character my own,” he says. “What’s so great about the MCU is it doesn’t exactly follow the comics, so you have the freedom to adapt characters. Jac and Mary were really great, and if I had an idea about something, I was very free to make Billy my own — and make him me.”

Episode 6 presented a particular challenge, as Locke had to play both Billy Maximoff and William Kaplan. The actor says he approached them as two entirely separate roles, wanting to explore each boy’s similarities and differences.

“I saw William as the lighter side,” he explains. “Billy is a much darker character. It’s almost like William is the Teen of the first five episodes, until you see the big shift and then the darker Billy comes through. He’s had to almost play the façade for his parents and be the son that they had for 13 years. The Teen part of Billy is that fanboy mask, and below that, you find Billy is much darker.”

Livanos says one of her favorite moments is the episode’s beginning, where William Kaplan prepares to celebrate his bar mitzvah with his parents.

“We really wanted to celebrate the beauty in this character,” Livanos says. “I just love how the episode opens with his bar mitzvah. Joe Locke has an incredible singing voice: He has the voice of a Disney prince, so to hear him at the beginning of the episode is such a striking way to open. But it’s great to finally get to know him as a character. It’s very satisfying after all the questions that are raised in prior episodes.”

For Locke, he’s just relieved that he can finally talk about who he’s playing — and the fact that it’s such a rewarding, challenging role. He teases that the upcoming episodes will explore Billy’s personality further, as well as his complicated relationship with Agatha.

“As an actor, it’s so fun to play someone who starts in such a different place than you end up,” Locke says. “The big question for me was: Is that Teen fanboy side a façade? Is it all fake, or is that a real part of him? How much is he playing Agatha, and what does he know?”

“Jac was really interested in playing the gray area of Billy as a character,” he adds. “He’s not all innocent. He does bad things. It’s whether that makes him a bad person, or whether he just has a darkness inside him. We had so many great conversations, and I felt so trusted by Jac, Mary, and all of our directors to play with that. It was so much fun as an actor to get to sink your teeth in a character that’s not one-dimensional.”

Agatha All Along is now streaming on Disney+.