Thirty minutes before showtime just about all the cast members of “Saturday Night Live” were gathered in a green room, going over their bits. “Fred, remember on the cold open, you wait for Darrell,” Seth Meyers, one of the show’s head writers, instructed Fred Armisen. Kenan Thompson ran his lines and brushed his teeth; Rachel Dratch adjusted her Debbie Downer wig; Kristen Wiig gathered her props. Norah Jones, a surprise guest, arrived and greeted the guest host, Michael Cera, the deadpan boy-hero of “Superbad.”

“Nice suit,” Mr. Cera told Mr. Armisen, who moments later doffed his pants and was standing spread-eagle, having clumps of fake hair applied to his buttocks. Mr. Cera read his cue cards a few feet away. Every few minutes Gena Rositano, a headsetted stage manager, called out the time. And then, at 11:37 p.m.:

“Live from New York, it’s Saturday night!” Mr. Armisen announced from the stage. Then came the usual mix of topical and ludicrous sketches, videos and music. Yo La Tengo sang.

But this NBC show was not live from Studio 8H in Rockefeller Center. Nor were there any television cameras. The continuing writers’ strike meant there could be no new broadcasts. Instead the cast, writers and a few key production staff members had gathered in a subterranean comedy theater in Chelsea to perform the show live on stage for an audience of less than 200, including a Who’s Who of downtown comedy. The TV audience got a rerun of a Nov. 3 show, but at the Upright Citizens Brigade theater there was a rare event born of hammy necessity, unexpected availability and good vibes.

“We’re like cranky trained monkeys if we don’t get to perform,” said Amy Poehler, who is also founder of the theater. “We all thought about what we’re going to do during the strike, and because we have no other skills, we just scraped this together.”