Hudson, N.Y. — “If anyone asks,” Aubrey Plaza said, “you’re my cousin Nina.”

“You’re from Philadelphia,” she went on, supplying more back story as she collected an iced coffee at a cafe on the main drag here. The fiction was necessary because Ms. Plaza, a “Parks and Recreation” star, was working nearby, on a movie with a closed set (or at least, closed to reporters). It was the second-to-last day of production, and Ms. Plaza was feeling a little loopy.

“We’re playing hooky,” she said as she strolled around unrecognized with her cast mate Max Greenfield (Schmidt on the Fox series “New Girl”). He was bearded; she was dressed in shorts and a baseball hat. “My character’s a loser, and I’m in character right now,” she explained, straight-faced. They took turns goading each other: “Ugh, I’m so embarrassed already,” he said when she told a meandering story. She borrowed $20 from him to pay for the coffee and pocketed the change.

And when Ms. Plaza returned to the set to have her hair and makeup done, she smoothly picked up the thread of her lie. “Can we get a chair for my cousin Nina?” she asked, and, with an air of familial duty, inquired about “Nina’s” summer.

Having studied comedy since she was a teenager, Ms. Plaza knows how far to take a bit. At 29, she is reaching new career heights, less than a decade after she got a foothold in television as an intern on “Saturday Night Live.” She worked in the art department, despite — or perhaps because of — her clear lack of interest in it. After five seasons as the similarly disaffected onetime intern April Ludgate on “Parks and Rec,” Ms. Plaza has several high-profile films on the horizon in which she stretches from drama to zombie. And for her first leading role, in “The To Do List,” out July 26, she creates what may be a new screen archetype: the randy, brainy, politically savvy teenage girl. She plays a strait-laced high school valedictorian determined to lose her virginity in the summer before college, drafting a YouPorn-worthy sexual checklist in the process. Set in 1993 but presented with a 21st-century feminist point of view, the raunchy coming-of-age comedy is the feature debut of the writer-director Maggie Carey, who developed it with Ms. Plaza in mind.