When it comes to comedy in Portland, stand-up gets most of the love. But nearly any weekend, you’ll find improv or sketch on some half-dozen stages around town—maybe an ad-libbed faceoff at Northeast Portland’s Curious Comedy Theater or Old Town’s Brody Theater, or a Game of Thrones send-up amid the creepy clown paintings of Funhouse Lounge. The Siren Theater, devoted largely to improv and sketch, opened late last year. Even the Portland Art Museum hosts occasional art-themed improv shows in its hallowed halls.

So when the Stumptown Improv Festival launched two summers ago, it seemed to arrive fully formed, capitalizing on a critical mass of high-quality local work. In its first year, the three-day fest—which features both Portland and out-of-town groups—drew audience waiting lists. In an expanded year two, six of its eight shows sold out.

“Last year was the, ‘Whoa, are you serious right now?’ moment,” says Leon Anderson, who founded the festival with fellow improv vets Jed Arkley and Erin Jean O’Regan. Anderson recalls showing up each evening to a swarming Milagro Theatre lobby. “I was like, who are all these people?”

“We tapped into an unseen need,” adds Arkley. “We showcased that improv is super-smart, and that you don’t have to call yourself an improv fan to like it.”

This year’s installment hops the river from the 140-seat Milagro to downtown’s 160-seat Artists Repertory Theatre—an upgrade modest in size but significant in sheen. Still, the festival remains a tightly curated affair, limited to a single venue. This year, 114 submissions from would-be participants flooded in, for only 18 spots.

Selectivity is one reason for the fest’s success. Timing is another. In August, big-name performers are less likely to be tied up in television casting. It’s also an easy time to attract out-of-towners. (Which isn’t to say Stumptown was a foreordained hit. Portland already has the popular Bridgetown Comedy Festival, and August events compete with swimming holes and backyard barbecues. In the first year, Arkley wore an elaborate stump costume to the Alberta Street Fair to attract audiences—an idea hatched during a long night of drinking at Reel M Inn.)

But just as improv swears by the rule of “yes, and ... ,” the local scene immediately ran with it.

“I was so excited,” says Curious Comedy artistic director Stacey Hallal. “It reinspires local performers and raises the bar of how good improv can be.”

Stumptown also helped jolt audiences. “Once the festival started, it was like this rock got lifted and people saw a whole world happening under there,” Hallal says. “It was too good to ignore anymore.”

Though the three organizers talk of tensions in the past, they still consider themselves something of a curatorial dream team. “When the three of us get together, our taste is awesome,” says Arkley, who’s drawn to groups that seem ready to spiral out of control. Anderson, who’s black—and says that before 2013 he’d never performed onstage with another black improviser—keeps an eye out for diversity. O’Regan, meanwhile, looks for action, movement, and prop work.

And they’re confident they’ve assembled another dud-free lineup this year. Local favorites include action thriller improvisers Bang + Burn, and the Liberators (Siren Theater owner Shelley McLendon is a member). The out-of-town groups read like improv royalty: freestyle rappers North Coast; husband-and-wife team Orange Tuxedo (Craig and Carla Cackowski, he of Community and Drunk History), and Canadians Sunday Service, which Arkley describes as “Kids in the Hall on cocaine.”

As with all improv, how it comes off remains to be seen. But Anderson, Arkley, and O’Regan have faith that this line of funny can bring something special to town.

“When it works,” O’Regan says simply, “improv is magic.”