PARK CITY, Utah – “Who’s that girl?” was a common refrain from Sundance Film Festival goers walking out of “My Old Ass” in January.

The comedic and heartfelt coming-of-age film, in which a small town 18-year-old eager to leave for college is suddenly in conversation with her 39-year-old self (thank you, mushrooms), was one of the breakouts of a strong festival. It’s currently playing in select theaters, expanding this weekend and next.

The girl in question is its vibrant star, Maisy Stella. It’s a name that will be familiar to some, for her years on the television series “Nashville” playing Daphne Conrad, for her viral video singing Robyn’s “Call Your Girlfriend” with her sister, Lennon Stella (31 million views and counting), and for being someone Billie Eilish has said inspired her to start singing. But to a certain subset of cinephiles, Stella seemed like a complete discovery and an exciting one at that.

Both designations work, in a way. Stella is reintroducing herself in her first film role after taking a few years off to just be a normal teen. She started on “Nashville” when she was 8 years old. At 15, she took a break from acting.

“I went back to school and made sure my head was nice and screwed on and just went to prom and did all that stuff,” Stella, now 20, said in an interview with director Megan Park earlier this year. “The second I turned 18, I was just like, I missed it so much and found such a new appreciation for it.”

In “My Old Ass”, she plays Elliott, a bisexual teen on a small cranberry farm in Canada who is ready for her life to start elsewhere. But her 39-year-old self, played by Aubrey Plaza, tells her to slow down a bit, appreciate the things around her in the moment, and stay away from a guy named Chad. It’s a part that many actors wanted.