Imagine that you're a teenager and you get tickets to one of your favorite artists, Taylor Swift.  I'm sure you'd be thrilled!  But, to have your heart throb join her on stage??????  Ok, maybe a little jealous, but ecstatic wouldn't even describe the feeling after that surprise!  Well, it happened in LA, and they sang "Baby", one of Justin Beiber's songs togther, further showing Taylor's talent.