Listen to your elders, even if they are 39-years-old.

“My Old Ass” is a coming-of-age comedy that loves the question about what you would say to your younger self. You could tell yourself to predict the latest Apple product or give yourself investment advices. Or you could tell yourself to be a better person. Now, that’s what the movie is more interested in, and it works.

We meet Elliott (Maisy Stella), who is preparing for college and beginning a new chapter in her life. To celebrate, she and her two friends Ruthie (Maddie Ziegler) and Ro (Kerrice Brooks) take boat ride to an island, listening to a little Nelly Furtado, and doing magic mushrooms. Those mushrooms, however, make Elliott see Aubrey Plaza next to her. She thinks her dad put her up to this, but she convinces the teenager that she’s her older self-her 39-year-old self to be exact. Or it could be the mushrooms talking. Bad Trip!

There’s an important distinction between being 39 and 49. If you’re 39, you’re still in your 30s. That’s what Plaza tells Stella. I know because I remember my parents telling me that even though my father was born in 1959, it would be proper to say that he was born in the late 50s, not early 60s.

She puts her number on young Elliott’s phone, under the name “My Old Ass.” So, maybe it wasn’t a hallucination. Could it also be a visit from the future like “The Adam Project” or “Happy Accidents?” Maybe. Could be a message from her universe? Anything is possible.

Does she tell her family she just met her older self? No, because it would be part of that long suffering cliche that they’re not supposed to believe that a fantasy is taking place. That is if this is a fantasy. It’s clear that writer/director Megan Park (“The Fallout”) has grown weary of the cliche, too, and refused to add it in her next feature. Her acting credits include “What If” and “Central Intelligence,” and her directing credits continue to prove she has a voice as a filmmaker.

Her advice to her younger self is to spend time with her family-consisting of farming parents Tom (Alain Goulem) and Kathy (Maria Dizzia) and brothers Max (Seth Isaac Johnson) and Spencer (Carter Trozzolo)-and avoid a guy named Chad. Who is her? Why should she avoid him? She doesn’t know, and neither do we. All we know is that a young man named Chad (Percy Hynes White) unexpectedly comes into her life. Yes, she’s shocked and needs some time to process. But does it have to be one of those ridiculous sitcom situations where the girl has to avoid the guy at all costs? No, it doesn’t. In fact, she finds him to be a likable guy. But we still wonder what Plaza’s deal with him is.

And given her romance with him, she also begins to question her sexuality, as she starts off in the film thinking she’s a lesbian.

Other than a few unnecessary spots, “My Old Ass” has a funny and strong notion regarding this youth genre. Is it a drug trip or an actual time travel mission talking place? It’s fun to make those guesses, and the results aren’t obvious, but truthful and consistent. Park also casts Stella and Plaza in universally memorable performances as the same person in two different ages, and they both have naturalism in their characters. They can start off being funny and then, they can be serious, and it’s well balanced.

Feeling a similar kind of magic as “Booksmart,” I found something funny and wise inside these female characters, and we, the audience, are able to acknowledge and relate to their directions in life. How will this young girl go through life knowing what she knows now? You leave that to her future.

In Select Theaters This Friday

Expands Next Week