Camp Rock on! Fans at Demi Lovato's Staples Center concert in L.A. on Saturday, Sept. 27, were treated to a very special reunion between the "Really Don't Care" songstress and her ex-boyfriend/Camp Rock costar Joe Jonas.

The former Jonas Brothers singer, 25, appeared onstage midway through Lovato's performance of "This Is Me," their duet from the 2008 Disney Channel movie on which they met. The resulting screams from the crowd were so loud that they drowned out Jonas' vocals. 

As seen in video of the reunion, the exes finished the song holding hands and then shared a friendly hug. After the show, Lovato, 22, shared a photo of them together via Instagram, with the caption: "Thanks @joejonas for the awesome surprise!! #staplescenter #4yrssincewesangtogether #demiworldtour." 

Jonas took to social media, too, posting a picture of them onstage, as well as a video of them rehearsing. "Surprise LA! @ddlovato thank you for having me," he wrote. "Tonight was amazing. Fun keeping this a secret."

The Disney Channel stars, who dated for a few months after costarring in Camp Rock 2, have remained on friendly terms since their split in 2010, around the time Lovato went through what she called a "nervous breakdown" and ended up in rehab for "emotional and physical issues." The former X Factor judge even showed her support for Jonas after he wrote a shocking tell-all essay about his past — and their tumultuous relationship — for New York Magazine last December.

"I want to commend him for how brave he was," she told Us Weekly at the time. "He never was able to share his side of the story. He kept it really quiet. I was going through my stuff, and he got blamed for a lot of it. We argue like brother and sister now. It's like, 'Dude, what were you thinking?' But it's all good. I was like, 'Don't be embarrassed or whatever. I still love you. We're still family. It's all good.'"