Since walking away from a $50 million TV deal more than four years ago, Dave Chappelle has kept a low profile, to say the least. Though he's showed up at the occasional comedy club and tried to set some joke-telling records with marathon gigs, the Ohio-based funnyman has mostly stayed out of the spotlight.

On Tuesday night, however, Chappelle proved he could still draw a massive crowd when he packed Pioneer Square in Portland, Oregon, for a free impromptu performance that drew thousands after word began spreading about the show via Twitter, Facebook and text-message alerts.

According to Oregon Live, fans started gathering before midnight on Tuesday in anticipation of the show, and Chappelle took the stage just before 1 a.m. Described as "one of the most remarkable spontaneous gatherings in Portland history," the flash-mob-style assembly was more spectacle than comedy show, as the tiny sound system Chappelle spoke through made his jokes inaudible to most of the crowd beyond the first few rows.

Well before he took the stage, the mostly 20-something throng nearly filled the square, bursting into applause when Chappelle finally strode in at 12:53 a.m. to a small stage that was still in place from the square's lunchtime concert series. Turning on an amplifier described as "the size of a toaster," Chappelle addressed the audience — most of whom could not hear him — thanking the Portland Police for being "kind enough not to arrest me."

Explaining that he was "not here for the money," Chappelle said he was happy to see so many people "stand this close together and not be angry." Oregon Live reported that one attendee said Chappelle had performed at a Portland-area restaurant called the Bye and Bye the night before, which explained why he was in town, but not why he chose to do the free public performance. Chappelle's official Web site has no official gigs listed for him at this time.

Most fans reportedly found out about the midnight show at the last minute after getting text messages from friends, and though Chappelle said he expected a few hundred to show up, the comedian, who arrived alone and with no security, was happy to see the huge crowd.

A fan climbed onstage at one point and announced that he was going to fetch a better sound system, but when he returned a while later he was thwarted by the fact that there was no power supply to plug it into. According to reports, the throng covered every square inch of the square, from the top of a Starbucks Coffee to the tin roof of a Shelly's Honkin' Huge Burritos cart, with the occasional woman flashing the crowd and Chappelle, and two men stripping at one point as the crowd egged them on.

Though the sound situation was never resolved, the crowd reportedly stayed calm as the occasional fan rushed the stage to shake Chappelle's hand or take a picture with him. At one point, some impatient folks up front rocked the stage and those around them shouted "No!" and booed the action.

"This has never happened in my entire career," Chappelle said as the audience burst into cheers. "I'm grateful everybody came out." As 2 a.m. rolled around, it became obvious that the sound system would not work, and after telling a handful of jokes, Chappelle thanked the crowd and revealed one of the lessons he learned while in town: "Don't tell a secret in Portland." Then, just as strangely as it began, the show ended around 2:09 a.m. when Chappelle left the stage and meandered over to a nearby hotel, where he chatted with fans for a while.