During an official Proactiv commercial shoot, customers were brought in under the assumption they were auditioning for a TV spot. Meanwhile, Justin sat behind a curtain, pretending to be their director.
In the clip, you can see the 17-year-old singer calling out silly directions and cracking up behind the monitors. He almost blows his cover a few times as he bursts out laughing.
Later, he surprises the girls by coming out and revealing himself. Naturally, each customer was shocked and excited. Check out how it all went down below, and see why Justin refers to himself as a "prankster on the loose."