*The president and first lady partied into the wee hours of the morning with friends and supporters at an ultra-exclusive inaugural gathering at the White House, where a DJ played “Love Train” and “We are Family” in the East Room.

The ultimate insider Inaugural event is the after-hours party that first couple hosts at the White House after all the formal balls, and this year, celebrities and California were on hand at the informal gathering that went past 3:00 a.m. on the morning of Jan. 22.

One long-time Obama supporter invited to the gathering told The Hollywood Reporter that between 150 and 200 invited guests mingled in the East Wing’s formal reception rooms with the president and first lady. As a DJ played songs by Michael Jackson and Stevie Wonder, Obama reportedly shed his coat and headed a conga line through the East Room.

“The first lady was right behind him,” the source told THR. “We were all in line dancing to ‘Love Train’ and ‘We Are Family.’ It was like a really great family party.”

The celebrity attendees included Ashley Judd, who was talking about running for Senate in Kentucky; Kelly Clarkson, who performed at the official inauguration; actor Wendell Pierce from “Treme;” talk-show host Steve Harvey; Eva Longoria, who skipped her own party to attend the event; Kerry Washington; singer Janelle Monae; James Taylor; Katy Perry and boyfriend John Mayer; and actor and former White House staffer Kal Penn.

Among the California and Los Angeles politicians invited were Mayor Antonio Villaraigosa, who is said to be angling for an appointment as Commerce Secretary; former Assembly Speaker Fabian Nunez; mayoral hopeful and City Council Member Eric Garcetti; labor honcho and incoming DNC Chairwoman Maria Elena Durazo; House Minority Leader Nancy Pelosi; outgoing Labor Secretary Hilda Solis, who reportedly will seek the county supervisorial seat Gloria Molina is about to vacate; former California State Controller and major Democratic giver Steve Westly; and Fremont Place residents Mattie and Michael Lawson. He’s a lawyer, and she is an interior designer.

Also among the guests were Senators John Kerry, Claire McCaskill and Tim Kaine; Massachusetts Governor and presidential pal Deval Patrick; Chicago Mayor and former Obama chief of staff Rahm Emanuel; outgoing Defense Secretary Leon Panetta; former Secretary of State Colin Powell; political strategist Donna Brazile; Cecilia Munoz; Valerie Jarrett; DNC Chair Deborah Wasserman Schultz; and labor heroine Lilly Ledbetter. The Castro brothers from San Antonio — the mayor and his identical twin brother, the new congressman — were distinguished only by the latter’s red congressional lapel pin.

Some of the president’s celebrity guests took to Twitter to extol the evening:

• Judd: “Hmmm. Does one use the front door at the White House?”
• Perry: “Just left the White House. All other parties from here on out will be judged unless they take place at the White House.”
• Clarkson: “Just partied at the White House … I kid you not, Michelle Obama stood up and got the party started … seriously cool First Lady.”
• Pierce: “Amazing day of celebration yesterday at the Inauguration of President Barack Obama. Honored to congratulate the President in person. History.”
• will.iam: I took my mama to the white house & every step I took I wanted to cry…I’m so proud of our past
• Monae summed it up with one word: “WOW.”