Partway through the coming-of-age film “My Old Ass,” 18-year-old Elliot (Maisy Stella) takes a boat ride with her crush. He muses about growing older, and wonders if he can pinpoint the final time he and his friends played make-believe before they grew out of the game.
That sense of time passing was what sparked Megan Park — the writer-director of “My Old Ass” — to come up with the film’s premise. An actress-turned-filmmaker, Park was visiting her childhood home in Canada when the idea began to percolate.
“I was thinking about how there was a last time that I slept under the same roof as everyone in my family,” she recalled on a recent Zoom call, “and then it was sort of this fantasy of, gosh, if I could go back and tell myself it was the last time, would that be a good thing or would it have just made me more anxious?”
In “My Old Ass,” that question comes to life after Elliot comes face to face with her older self during a mushroom trip. The 39-year-old Elliot (played by Aubrey Plaza) shares some life advice, including that Elliot should carve out bonding time with her mom and brothers. But the older Elliot also warns her younger self to stay away from a boy named Chad — although she refuses to tell her why.
The story takes place in Muskoka in Ontario, Canada, during Elliot’s final summer before college. Passing the days on her parents’ cranberry farm or boating around the local lake, Elliot is more than eager to leave the confines of her small haven. But over the course of the film — and with some wise counsel from her older self — Elliot comes to appreciate the poignance of saying goodbye to the place she has always called home.
Park grew up spending summers in Muskoka, and has fond memories of its natural beauty. The cranberry farm was “a beautiful setting that I hadn’t seen before, and I knew it was very authentic to that part of the country,” she said. “I wanted to see somebody in a cranberry bog, corralling cranberries. It’s so cool.”
Her team shot on location at a local cranberry farm but had to cheat one aspect: The berries wouldn’t rise in the bog until later in the season. For a scene in which Elliot wades into the bog during harvest time, Park’s team found an empty marsh and dumped 30,000 pounds of frozen cranberries inside.
The setting lends a note of specificity to the story that’s matched in the performances. Stella, who plays the younger Elliot, had never acted in a film before “My Old Ass,” although she had contributed a song to Park’s first film, the 2021 drama “The Fallout” and knew Park socially.
When the pair first met, Park took note of how Stella was “very bubbly and outgoing, and full of spark.” These were qualities Park wasn’t used to seeing in young female characters, who were often written as more brooding or emotional, she said.
There were other auspicious signs that Stella was right for the role: She was from a Canadian town close to where Park had grown up, and she owned a boat, just like Elliot. Park knew she’d found her star.
“Elliot is somebody who’s so mature and wise beyond her years, but also youthful and wide-eyed and vulnerable at the same time,” she said. “Maisy calls herself clinically nostalgic,” she added, which made her a good fit for a story about personal growth.
Casting the older Elliot was the greater challenge. Originally, Park had written the role as being in her late 40s or early 50s. During casting, they spent a lot of time searching for actresses who resembled Stella, and thus could conceivably embody her older version.
“For some reason, nothing was clicking in my brain. And we were like throwing around ideas, and I saw Aubrey’s name. And it truly was a lightbulb moment,” Park said.
Previously, Park might have ruled Plaza out, since the pair didn’t look much alike, and Plaza was only in her late 30s. But once they found out Plaza was interested, the dynamic snapped into place. “The title was funnier to me. The back and forth was funnier,” Park recalled. “It works in a way I can’t explain.”
To a teenager, even a 39-year-old version of herself is her old ass.
Park also carved out space for improv between the actresses. One of her favorite unscripted moments is a kiss that the Elliots share upon first meeting.
“I said to Aubrey, what if she asks you if you can kiss her? Like, are you down?” Park recalled. “Because I knew it was going to be Maisy’s literal dream.”
Sure enough, Stella, a huge Plaza fan, took the plunge in the next take.
“Maisy’s genuine response was, ‘That was the best moment of my life,’” Park said with a laugh.
Park’s early acting experience in TV shows such as “The Secret Life of the American Teenager” makes her ideally suited to write and direct teen movies. As someone with experience performing lines written by adults, she knows how quickly inauthentic dialogue can tank a storyline.
Her trick for writing teens, she said, is to ignore age entirely. “I wasn’t trying to make a movie about young people,” she said. “That’s what people get wrong: They’re trying to force-feed a tone or a message.”
She added, “Young people can sniff out stuff that’s trying to be for young people, instead of just being human at the end of the day.”
Natalia Winkelman is a film critic based in Brooklyn, N.Y. Follow her @nataliawinke.