Ok, so we've had the Bieber fever for quite some time now, and as much as we love his pop songs, THIS took our fan girl status to a whole new level!

On Tuesday night Justin Bieber stopped by State Social house, and rather than causing chaos, the 20-year-old pop superstar took the stage and gave an amazing acoustic performance of "I'll Be" and "Home to Mama."

According to sources at the West Hollywood hotspot, Bieber just happened to grab a guitar and sing a few songs -- this was not planned. Um, maybe he should plan more of these, because a) they'd sell out in a heartbeat and b) we love this more mellow sound! Maybe that's what he's working on with super producer Rick Rubin?

Check out the video above and tell us what you think about his stellar set!