The kids of PS 161 in Harlem got a huge surprise yesterday when doing a choreographed dance to one of Beyonce's songs -- Beyonce herself!

While the group was midway through a routine for "Move Your Body," Knowles popped up out of nowhere and joined on in. The reaction shots on some of the kids' faces are priceless.

The dance was part of Michelle Obama's "Let's Move" initiative, where schools around the country simultaneously broke into the routine to promote the fight against childhood obesity.

Hot Videos