jeans Justin Bieber leather concert acoustic

Justin Bieber arrived at NBC studios yesterday for an appearance on The Tonight Show with Jay Leno, and not only did the 18-year-old pop superstar pose for photos with his adoring fans, but he gave them an impromptu acoustic performance of "Boyfriend"!

Bieber pulled up in his tour van, and after the screams died down, he started singing along with the crowd, taking some time at the end to sign autographs and shake hands. What a sweetie! No wonder Selena Gomez is head over heels for this guy...

Check out the video below!