Before you start freaking out, no, Lance Bass has not left N*SYNC to become a Backstreet Boy.....BUT he did perform with them for one night!

The Backstreet Boys are in Vegas right now for their residency and last night they had a special visitor, Lance Bass. TBB brought Lance up onstage to help him sing their hit song "Shape of My Heart" and girls everywhere were excited to see 2 historic boy bands coming together. Check it out....