Bieber Fever
Justin Bieber joins Grande onstage during weekend two of the festival in what was apparently an impromptu performance. "I had no idea I was gonna be on a stage tonight, absolutely no idea," he tells the roaring crowd. "I had to get my groove back, I had to get my swag back, you know what I'm saying?" The "Sorry" singer also promised some new music and an album would be "coming soon."
Grande Style
As if guest appearances, choreography, a dazzling set and tons of hits weren't enough, the star also changed several times, giving fans a fashion show to boot.
Making Moves
The star certainly had her dancing shoes on as she tore up the stage with plenty of impressive choreography.
Tearin' Up Our Hearts
Grande proved she could be the fifth member of *NSYNC when the former boy band members JC Chasez, Lance Bass, Joey Fatone and Chris Kirkpatrick joined her on stage for a rendition of their signature hit, "Tearin' Up My Heart." Needless to say, Grande and the group were totally in sync.

