It's never nice to pick on your friend's younger sister, you know. Poor Willow Smith has enough on her plate pulling civilizations out of the dust and practicing the final note on her rendition of "Tomorrow" without being subjected to that kind of bullying. But Justin Bieber, ever the high schooler, just couldn't leave well enough alone. So when his buddy Jaden's younger sister was opening for him on the Manchester spot of his My World tour, The Bieb decided that it was time to pull a little prank on young Willow.

First up came Bieber's manager Scooter Braun and swag coach Ryan Good, who rushed the stage during Willow's performance of trademark hit "Whip My Hair" with long and weirdly-colored wigs on, trying to disrupt the child pop star. When that failed to throw the pro's pro off her game, out came Justin himself, dancing around the stage and wailing on a cowbell like he was in Grand Funk Railroad. Just in case there were any teenage girls in the audience who had managed to maintain consciousness until that point, he threw in a couple hair-whips himself for good measure. (Though, to be honest, it probably would have worked a lot better for Bieber pre-haircut.) And then finally, in came big bro himself, with Jaden sporting a big-ass fro much more condusive to hair-whipping. MOOOOOOMMMM!!!!

Willow, for her part, is not taking the attack lying down. "They got me, but it's not over," swore the 21st Century Girl backstage after the show. "Revenge is sweet, and it's served on a cold dish." (Uh, close enough.) Better sleep with one eye open (and some sort of protective hairnet on) for the next few weeks, Justin.