Justin Bieber Gets the Giggles in Concert (VIDEO)

Justin Bieber’s concert in Pittsburgh on Monday was apparently a roller coaster of emotions.

The 16-year-old My World singer was forced to temporarily halt the show at the Consol Energy Center when a group of fans began fighting over a towel that he threw into the audience. After successfully mediating the argument, the Biebs launched back into his song “Baby,” but apparently the plea for peace managed to throw him off of his game, because the song quickly fell apart as Bieber fell victim to an uncontrollable giggling fit.

Maybe he was struck by memories of just how silly that drawn-on mustache of his looked?

Watch Bieber turn his concert into a laughing stock below. What do you think he was giggling about? Share your theories in the comments section.