Our friends send us funny YouTube videos of animals, babies and sometimes themselves, but when Justin Bieber appeared on our computer screens, everything changed. He went from YouTube sensation to Usher's protégé to Twitter's number one trending topic in a matter of a few months and now it's hard to even imagine our lives without him! We're looking back on some of our fave Bieber moments ever before we get tickets to see him in concert! Click to watch some awesome YouTube clips and click here to find out how and where you can see him this summer!

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