The duo sang a duet of "Yeah!" and introduced MC Hammer.
Justin Bieber's manager, Scooter Braun, threw his 30th birthday party Saturday and he pulled out all the stops for the Hollywood bash, Radar Online reports. Usher and Bieber performed a duet of "Yeah!" while the teen pop star played the drums. Then they introduced surprise guest MC Hammer.
The party featured a carnival theme with contortionists, tarot card readers, fire throwers, beer pong and pole dancers. Even Bieber and Will Smith's son Jaden got in on the beer pong, but don't worry, it was a kid-friendly version. Which begs the question: where were they during the pole dancing performances?
Other guests included Kim Kardashian, Paris and Nicky Hilton, Rita Wilson and Maroon 5's Adam Levine who performed the group's hit song "This Love."
(Photo: Alberto E. Rodriguez/Getty Images)