Megan Park loves hearing how much old dudes adore “My Old Ass.”

The writer/director’s new coming-of-age dramedy might be humorously titled, but it’s touching multiple generations. After the movie premiered at Sundance Film Festival, Park had 70-year-old guys coming up to her and saying how much they liked the story of a teenage girl meeting her 39-year-old self.

“I wasn't expecting them to be as moved,” she says. Her star, Maisy Stella, “will always send me Letterboxd reviews like an 18-year-old posting, ‘Not me and the 65-year-old dude next to me crying in the movie’ in a really sweet way.”

That shared emotional connection is the secret sauce of “My Old Ass” (in theaters now), which tackles teen themes of sexuality and family ties with a twist. Stella stars as Canadian youngster Elliott, on the cusp of adulthood and spending one last summer at home. On her 18th birthday, she and her besties camp out in the forest and take mushrooms to celebrate. While Elliott’s pals have their own trips, she winds up on a log suddenly conversing with an older Elliott (Aubrey Plaza) who’s pushing 40.

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They strike up a summertime friendship with much texting and phoning. Teen Elliott wants to know what happens in the future. Her older self says she should hang out with her mom and brothers more and warns her to stay away from anyone named Chad. Young Elliott considers herself a lesbian but starts questioning that when she actually meets Chad (Percy Hynes White), and both Elliotts learn from each other as one begins to chart what’s next and the other comes to grips with her past.

“Getting to go back and either relive a day or have a conversation with your younger self or say something that you wish you would've said, those things really cut to the core of all of us as humans,” Park says.

The idea for “My Old Ass,” produced by Margot Robbie, came to Park when poking around in her childhood bedroom. She found a letter from summer camp written to herself one year in the future. “It'd be like: ‘OK, this is me in seventh grade. Next summer when I come back here I'm going to be in eighth grade, and who am I going to be?’ These sort of big existential questions coming from a 12-year-old, which I thought was pretty funny,” she says.

Park figures she could have heeded some of her future self’s advice at 18: “I was so dumb and out to lunch when I was younger.” But now at 38, she has proven adept at tapping into the voice and culture of the next generation. A former actress who starred on "The Secret Life of the American Teenager," Park had her directorial debut with the 2022 school shooting drama “The Fallout."

“Megan approaches writing for Gen Z in a way that feels smart,” says Stella, 20. “She doesn't fall into the stereotypes of the teenager being so mean to their moms or they can't look up from their phone or making a TikTok.

“She just writes for people who happen to be young. As a young actor, Megan's writing is literally the holy grail.”

At screenings, Park has been keen to learn what all ages take from “My Old Ass.” Kids feel it’s authentic to “how they speak and talk,” the director says. “Some of the queer conversations really spoke to them, and this idea of anxiety around leaving home for the first time really resonated."

And for older audiences, “there was this sense of nostalgic longing that had a heaviness that maybe you just don't inherently have when you're 18,” Park says. “There is more of a sadness but a happy sadness.”

In one thoughtful scene, older Elliott tells her younger self, “The only thing you can’t get back is time.” It’s a line born from the experience of raising her 4½-year old daughter, Winnie, with her husband, musician Tyler Hilton. 

“I remember being pregnant with her and people saying: ‘Blink and you'll miss it! Don't look away − you'll turn back and they're 10 years old.’ And it's like, ha ha ha, old asses giving me advice (but) it is so true,” she says.

Recently, Park saw “My Old Ass” again for the first time since giving birth to her second child, son Bennett, in July – two weeks after losing her dad.

“I found myself wanting to cry so many times in the movie. And I was like: ‘I can't cry at my own movie. That makes me seem like such a psychopath,’ ” Park says, laughing. "It's been so wild to see people of all ages responding to this movie in the same way. The theme of just time passing and regrets are so universal."