You can't prank a prankster, and Miley Cyrus learned this one the hard way. She thought she was going to punk Justin Bieber, but sadly (at least for the 'Can't Be Tamed' songstress), he was in on the joke the whole time. The former Disney starlet's face is absolutely PRICELESS when Bieber comes out to reveal his part in the show.

Take note, Miley! Justin is impervious to pranking!