And he jammed with former US President Bill Clinton at the 1993 inaugural ball.
The "Red, White and Blue Inaugural Ball" and "Hip-Hop Inaugural Ball" closed out Sunday's activities.
The Red, White and Blue Inaugural Ball and Hip-Hop Inaugural Ball are also scheduled in the capital.
The Obamas also danced to "Let's Stay Together" at the Inaugural Ball, also held in the convention center.
The Inaugural Ball was split between two floors in the building, and attendees were not allowed to go from floor to floor.
Indeed, individual tickets and bundled tickets to the official Inaugural ball have been going for thousands of dollars on both eBay and Craigslist.
Big-ticket items will likely be a coveted invitation to the network's annual Video Music Awards or an invitation to an inaugural ball next January in Washington.
The private university is consistently ranked as one the most politically active in the country and, every four years, during the presidential inauguration, it hosts the black-tie GW Inaugural Ball.
Ayman Hakki, a cosmetic surgeon who has lived in Washington since the Kennedy administration, runs a Georgetown walk-in clinic that he says is jammed with inaugural ball attendees seeking last-minute Botox.
WSJ: Wardrobe Dysfunction: Inaugural Puts Button-Down Town in Tizzy
The Huffington Post, the news aggregation and commentary site, is hosting a pre-inaugural ball Monday night with the Atlantic Philanthropies and the Musk Foundation, which supports research on renewable energy, human space exploration, and pediatrics.
Wu, whose dress was among more than 15 custom designs for the First Lady to choose, was also the winning designer four years ago when Michelle Obama wore his white one-shouldered gown to the inaugural ball.
FORBES: Michelle Obama's Red Is The New Black -- For Retailers
The kids will perform Tuesday at the Africa and International Friends Inaugural Ball, sharing a stage with Usher and Patti LaBelle, one of many events in their packed schedule highlighted by a luncheon gala Monday to honor the Rev.
CNN: Bringing song to Obama's inauguration, students savor fame
On Monday, the Creative Coalition was putting on a ball with a performance by the Goo Goo Dolls, while the Young and Powerful Black Tie Ball and the Congressional Black Caucus Inaugural Ball were also taking place in the city.
The event was just one of will.i.am's inaugural appearances: He's attending the Candle Light Inaugural Ball and Green Inaugural Ball on Sunday and will be a guest at Obama's public swearing in ceremony Monday and at the Inaugural Ball later that day.
There was one reason -- I used to say to Governor Markell of Delaware -- why I never ran for governor -- you have to have an inaugural ball. (Laughter.) And that's why I stayed in the Senate all those years.
Plenty of other parties will be celebrating a renewed commitment to the environment, including the Green Inaugural Ball, chaired by Al Gore and hosted by a number of organizations like the American Council on Renewable Energy, the Energy Action Coalition, and the Vote Solar Initiative.
"On Sunday evening, Ticketmaster experienced a technical error that inadvertently caused an e-mail to go out ahead of schedule to people who had signed up for Inaugural ticketing information with an invitation to purchase public tickets for The Inaugural Ball and the Inaugural Parade, " the spokesperson said.
Run by the committee, proceeds will help fund other events like the Inaugural parade and ball.
Equally effusive was "Glee" actor Darren Criss, who attended the ball and had performed over the weekend at the Kids' Inaugural Concert.
应用推荐