Every revolution starts with a single act. Unless it doesn’t. At 6:15 p.m. on Aug. 14, a group of five people starts playing rock-scissors-paper in Farragut Square. On the other side of K Street NW, separated from the square by rush-hour traffic, the after-work crowd busily streams into the Farragut North Metro station. The District’s first “flash mob” has touched down, unwatched.

This is how it’s supposed to work, in cities around the world: Groups ranging in size from dozens to hundreds, given marching orders via e-mail forwarding, converge on a random place, make a scene for a little while, and then leave. In New York, where such impromptu groupings began in June, mobsters have shopped for a “love rug” at Macy’s and made bird calls in Central Park.

Zany spontaneity, however, requires careful planning. The organizers of the District mob, who call themselves the Society for Spontaneous Congregation (aka Woodley Park roommates Chad Poist and Andrew Blackwell), demand professionalism and precision from their charges. “Please arrive exactly at 6:15,” their e-mailed invitation, sent the night before, instructs. “At exactly 6:15, you will begin playing rock-scissors-paper on the corner.”

At exactly 6:15, the 31-year-old Poist charges onto the grassy area inside the square, eyes bright. “Rock, scissors, paper, go!” he booms, his fist slapping into his palm. The other four members of the mob are less confident. “Should we do it now?” someone asks. “Let’s wait for Andrew,” suggests another. Blackwell is late. He shows up a moment later, and the group soon swells to nine, then—with more arrivals at 6:18—to 13.

Conversation drifts towards the manifold differences in personal rock-scissors-paper style. Eventually, the group seems to agree on “1, 2, 3, go,” though there’s still a lingering difference of opinion on whether you should reveal your hand on “3” or “go.”

At 6:20, Poist yells out “Tournament! Play to five!” Everyone finds a partner and starts going at it, brandishing a scissors, chatting about the day at work, pounding down a rock.

Blackwell and Poist are among the early-round losers. Retreating to the sidelines, Blackwell says he needed a better playing strategy. “I was a little bit impulsive. Maybe I should have planned more,” says the 31-year-old Blackwell, adding that the same regrets apply to his nascent career in flash-mob organization.

“If you’d ask me, I’d guess it started in Japan,” Poist says, standing watch over the last few minutes of his first mob. “I lived in Japan for a while, and they’re good at this sort of thing.” (In fact, the phenomenon got its start this past June in New York.)

The last match in the winner’s bracket—played to seven—is a nail-biter. Mary Kay Griffin leads 6-5 before a string of rock-rock, paper-paper, paper-paper gets the crowd “ooh”-ing! and “eeh”-ing! Then Griffin shows rock; her opponent shows scissors. Griffin wins, 7-5.

“I’m just psychic,” the 28-year-old Griffin explains, before delving further into her strategy. “You’ve got to mix it up with doubles. Paper, paper.” At 6:24, most of the crowd disperses, as per the plan. Blackwell, Griffin, and Poist drift over to edge of the square to collect their bikes. Poist rides away at 6:28. “I have an Ultimate Frisbee game,” he says. “I’m late for it.” CP