Justin Bieber pulled a fast one on Willow Smith. The “21st Century Girl,” who is opening for the teen idol on the European leg of his “My World” tour, got quite a surprise during a performance of her smash “Whip My Hair” in Manchester, England, on Sunday night.

While Willow whipped her hair back and forth, Bieber’s manager Scooter Braun and swag coach Ryan Good slapped on some makeup and wigs and crashed the performance. The Canadian heartthrob soon joined in on the fun, rushing onto the stage and banging the cowbell to her hit.

After being punked, the 10-year-old singer is plotting her revenge. “They got me, but it’s not over. Revenge is sweet and it’s served on a cold dish,” said a scheming Willow backstage.

[Ryan Seacrest]