Patti Harrison, the actress and comedian, has taken one acting class in her life, an introductory course at Ohio University. “It was taught by a grad student and was very loose,” she said. “We mostly just did yoga.”

One assignment was to perform an interpretive dance based on a poem. Harrison searched online for “dumb emo poems” and found one called “A Darkness Inside Me.” “Looking back on it now, I think it was about someone who’s an active shooter,” she said. “I did it as a joke, but no one took it as one.”

Not many of Harrison’s jokes have fallen flat since. “Scene stealing” is one of the adjectives most applied to Harrison, who has appeared in alt-comedies like “Shrill,” “Search Party” and “Made for Love.” The downside of stealing scenes, of course, is that you generally don’t steal them on your own show. “I haven’t been in a million things,” she said. “And most of them have been really small, or guest parts.”

This week, Harrison, 30, moves from one-offs and recurring parts to her first starring role in a feature film, in “Together Together,” one of the breakouts of this year’s Sundance Film Festival. The dramedy stars Harrison as a 26-year-old barista named Anna who is hired as a gestational surrogate by Matt, a single 40-something app designer (Ed Helms) who really, really wants a baby — as well as some sort of connection with the woman who’s having it.

Harrison has already earned rave reviews, with critics describing her performance as “groundbreaking” and “revelatory”; The New York Times called the movie “sweet, sensitive and surprisingly insightful,” praising Harrison’s portrayal of Anna and her rapport with co-star Helms.

“Patti was the actress for the part,” said the director Nikole Beckwith. “And to get her in her first leading role, I just feel like the luckiest person on Earth.”

In a recent video interview, Harrison was in her home in Los Angeles talking about her childhood interests (there were many), the questionable roles she’s been offered as a transgender actress — “the first thing producers see in me is like, I’m trans” — and how “Together Together” came to be.

The stories come fast and looping. Ask Harrison what she was into as a kid, and you get the full menu, in chronological order, from age 4 through high school: sharks; dinosaurs; insects/arachnids; Pokémon (I was super, super into Pokémon”); video games; karate (“I was like, if I ever have to beat up 20 people at one time for absolutely no reason at all, I want to be able to do that”); guns; cars.

Harrison, whose mother is Vietnamese, grew up the youngest of seven siblings in a rural, conservative town in Ohio called, of all things, Orient. “I looked at the census when I was in high school, and it said there were zero Asian people in Orient,” she said.

In college, Harrison joined an improv group at the prompting of a friend. She felt an immediate connection — the tightrope feel of it, the magic moments springing seemingly out of nowhere. “It still triggers a lot of anxiety in me,” she said. “But when it goes well, it’s amazing. You can make up stuff, and things can seem brilliant on accident. People will imbue intention into everything that you do.”

In 2015, Harrison moved to New York and began doing standup comedy. There, she found fellow funny people like Julio Torres (“Los Espookys”), Jo Firestone (“Shrill”), and Ziwe Fumudoh, who recently filmed the music video “Stop Being Poor” with Harrison for her self-titled Showtime variety series. “Patti’s comedy comes from such a pure creative place, where she never does exactly the same thing twice,” Fumudoh said. “She’s phenomenally creative and original.”

In 2017, Harrison was recording a commercial when she got a call from “The Tonight Show” to do a bit for the show that night about her reaction to Trump’s just-announced ban on transgender people in the military (“I was shocked,” she said in the bit, “because I assumed he already did that.”) After the appearance, things exploded for Harrison. “My agent was like, there’s all these people who want to meet with you now,” she said.

“But at the same time,” she continued, “there were a lot of people I felt that had pigeonholed me into this idea of what they thought I was. They were calling me an activist without any prior knowledge of me other than this piece, because I’m a transgender person who had spoken on something.”

So while the appearance got her noticed, it was a very specific sort of notice, at least at first. In those early meetings with production companies, Harrison was brimming with pitches like, say, the one for a show about a dog and its dysfunctional, codependent relationship with the little bird that lives in his rectum. (“I gave them my gold ideas,” she said.) But all they were interested in were “stories about trans girls coming out and getting rejected by their families,” she said, or having her come on shows to talk about the difference between being gay and trans.

All of which made “Together Together” that much more special. Here was a story about a clearly cisgender woman — the plot revolves around her character’s pregnancy, after all — in which the relationship between the younger woman and the older man is much more nuanced than one sees in a lot of rom-coms. Not as much will-they-or-won’t-they, and more: Where does all this lead, if anywhere?

“It really takes a lot of humility to engage in a story like this, and Patti is very humble, and always authentic,” Helms said. “But then she’s also one of the funniest human beings on Earth.”

The film came at a time when Harrison was at a crossroads in her life. “I didn’t know if I was going to go into acting more, or kind of lean into TV writing or comedy,” she said. “And I was processing a lot of feelings about my self-esteem, and body dysmorphia. But then I got the script, and it was very delicate and positive and sincere, which is the opposite of what I normally do in my comedy stuff.”

Beckwith, the director, had spotted Harrison performing on a late night show and realized she had found her Anna. Harrison had an “amazing, salty, a little spiky, humor and way about her,” Beckwith said, that went hand in hand with her vision of Anna as “warm, like Patti, but not a totally open book.”

“Together Together” was shot in just 19 days in the fall of 2019, with limited chances for retakes. “The scene where her water breaks — that was our version of a stunt,” said Beckwith. “And we only had two pairs of pants, so we could only do it twice.”

Playing the lead “was very scary,” Harrison admitted. “But if I had known how much work it was going to be, I would have been way more scared. I think I was shielded a bit by being stupid about it.”

Harrison is getting fewer pitches for trans-centric roles nowadays, and she is busier than ever. In addition to “Together Together,” she is appearing in the final season of “Shrill” and singing, dancing and acting in “Ziwe,” and recently she joined the cast of the feature film “The Lost City of D,” alongside Sandra Bullock and Channing Tatum.

Still, that doesn’t mean her days of being typecast are over. “Now I’m seeing a trend where people want me to read for stuff where I play a social media-obsessed millennial, this vapid turd person. So I’m moving away from offers where, ‘you’re a de-transitioning sex worker who finds that he likes his old lifestyle a little better than she thought,’ to ‘you’re one of the stupidest people on Earth. You only like social media and likes.’”

The confidence Harrison gained from going “so far out of my comfort zone” has only fed her desire to move even farther out of it. What she’d really love to do is some sort of science fiction movie, the more action the better, she said, where she might indulge her childhood love of karate and get to say stuff like “zorbon crystals.” “I think there will always be a part of me that kind of fanboys out about action sci-fi,” she said, “just to see if I could do it.”