Biebs, you screwed up. When MMA champion Ronda Rousey comes up to you at a party in Cannes, you better snap to attention. Especially if she has her little sister with her! 16-year-olds are the only people who look up to you. If you've got the time to alienate a teenage fan, you've got time to pose for a photo instead. But pop star and guy who can cry on command Justin Bieber does not read Mixed Martial Arts Weekly (a magazine we just made up, but sounds like it exists), so he didn't know who he was messing with. Listen to Rousey tell this terrible tale:

Sources: Cosmopolitan