Brown, 20, surprised guests at West Hollywood hot spot Guys and Dolls with an impromptu performance of Michael Jackson's "Dirty Diana," Usmagazine.com has confirmed.
"He stood up on the back of the booth when the song came on, got a mic and not only sung, but danced his a-- off," clubgoer Cory Honickman tells Us. "It was insane and no one could look away. He is incredibly talented."
When he finished, Brown told the crowd, "There was only one King of Pop. We love you, Michael."
Brown is due to report to probation in 72 hours following Tuesday's hearing.
In addition to his 1,400 hours of community labor (Brown will remove graffiti and wash cars), the singer also must attend a year of domestic-abuse counseling and pay a number of fees and fines, while also being subject to random searches and seizures.
He also must stay away from Rihanna for five years, until Aug. 25, 2014, when his probation period is over.
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