HollywoodLife.com gives you the first inside look at the Jonas Brothers and Demi Lovato’s exciting impromptu performance at the Camp Rock 2: The Final Jam premiere Aug. 18 in NYC!

As if watching the world premiere of Disney’s Camp Rock 2: The Final Jam at the Lincoln Center in New York City with the stars of the movie wasn’t cool enough, mega fans were also given the treat of a lifetime: a live surprise performance by the Jonas Brothers and Demi Lovato – and HollywoodLife.com was there for it all!

After the movie — which hits the small screen Sept. 3 — an announcement came over the speakers asking the packed auditorium to stay in its seats for a special performance.

The crowd went crazy as Demi Lovato, dressed in a pink mini dress, sang and danced with the cast of the film. As the 17-year-old starlet was leaving the stage, the curtain began to rise and there stood Nick, Joe and Kevin Jonas, beaming from ear to ear.

After singing a few songs, the brothers decided to extend their performance and invited Demi back up to the stage. Unfortunately, she didn’t have a microphone, so Joe — her ex-boyfriend — joked that they should share. Demi shook her head no…and we could cut the tension with a knife! It was obvious that Joe, 21, was making a major effort to be nice, which made the whole thing much more awkward.

Luckily, a stagehand gave Demi a microphone and everything was business as usual for their duet from the movie, “Wouldn’t Change a Thing.”

Throughout the entire night, Demi, Nick, Joe and Kevin thanked Disney for its unending support — and Demi admitted being a part of Camp Rock was the best experience of her life! Will YOU tune in for Camp Rock 2: The Final Jam Sept. 3?

–Bonnie Fuller & Kirstin Benson