At 10, Arabella Olivia Clark Toppled the Box Office With 'Other Mommy'

Arabella Olivia Clark's first leading role debuted at No. 1, earning $12.6 million domestically on its opening day. She is 10 years old.

Rob Savage's "Other Mommy" opened in theaters on Friday. Clark plays Bela, the daughter of Ursula (Jessica Chastain) and Russ (Jay Duplass), terrorized by a sinister doppelgänger of her mother. It is her first time leading a feature film.

The morning after the premiere, Clark spoke to Variety over Zoom from her Los Angeles hotel room, wearing a jacket with her character's name printed on the front. Her mother, Rachel Clark, joined off-camera.

The takeaway: a first-time lead, a No. 1 debut and an eight-figure opening day — all before she turned eleven.

How does a 10-year-old prepare for a horror lead?

Clark read the film's source material, Josh Malerman's 2024 novel "Incidents Around the House," in three days — before she even landed the role. By her second audition, she knew the story inside out. It still unsettled her. "I got chills!" she said.

She is not easily frightened off screen either. "I love spiders. I love snakes. I like all the creepy stuff," she said. "I love the dark, so I don't really know what I would be afraid of."

Rachel Clark said nothing overtly frightening has ever held her daughter back. "She's always willing to try everything," she said. "Even if she can't do something, she's like, 'Yeah, I'll try that.'"

Off set, Clark takes sailing and swimming lessons. The swimming paid off during production.

What happened inside the 20-foot water tank?

One of the film's sequences required Clark to film in a massive water tank — 20 feet deep, pitch black, according to her mother.

Rachel Clark described it as one of the scariest moments of the shoot to watch. "There were balls. She had that Sherpa hoodie on, pulling her down, and they had the pyrotechnic people where there was an explosion in the water," she said. "The timing and everything was so well orchestrated. But of course, as a mom, it was very anxiety-producing."

Arabella's verdict: "It was fun. I love swimming, and I love being in deep pools. I can dive down all the way to 10 feet!"

She also performed her own stunts, including flips, spins and acrobatics.

What did Jessica Chastain teach her?

Clark spent time with Chastain and her children between takes. "Working with Jessica Chastain was a great experience," she said. "I spent time with her and her kids, and she's a great mom. We were always going to the park and hiking and all that stuff."

Chastain was also studying for Harvard while filming. "I can't believe it!" Clark said. "She's a mom, and also studying for Harvard and also filming a movie at the same time. I learned a lot from her."

Clark's favorite set memory: Chastain's witch cackle. "She's like, 'OK everybody, it's going to be loud.' And she did it, and I was so surprised," Clark said. "She could be a witch in a movie."

Director Rob Savage, Clark added, made sure she felt safe on set, while Chastain and Duplass kept the mood light with jokes and stories between takes.

Who is Mckenna Grace in her life?

Mckenna Grace, the former child actress, reached out to Clark directly and offered to mentor her.

"Mckenna Grace is so sweet. She reached out to Arabella and offered to mentor her and be there for her to talk about things like growing up in the industry," Rachel Clark said.

The two have so far only spoken online. "I'm hoping to meet her in person!" Arabella said.

What comes after 'Other Mommy'?

Clark previously played a younger version of Amanda Seyfried's character in the 2025 film "The Housemaid," directed by Paul Feig. She names Seyfried as an actress she will always look up to.

Of her two characters in "Other Mommy," the evil version was the clear favorite: "Other Bela!"

Horror is not her only target. She wants to move into science fiction — ideally a sequel to "E.T.," which would fulfill her dream of working with Steven Spielberg. "Maybe Rocky and E.T. could be friends, because they're both aliens, right?" she said, referencing the alien from "Project Hail Mary," which she loves alongside "The Meg."

Her reading list skews spooky too: her favorite book is "Bunnicula," the vampire rabbit, and she is currently working through one of Jeff Kinney's "Awesome Friendly Spooky Stories" books.

With a No. 1 debut, a box-office-validated lead performance and a mentor in Mckenna Grace, Clark enters her next decade with a genre credential most actors spend decades building — and she says she is just getting started.