The band — consisting of brothers Joe, Nick and Kevin Jonas — kicked off their 20th anniversary tour on Sunday at MetLife Stadium in their home state of New Jersey. But to make it more special, they surprised their fans with some special guests throughout the show, including Demi Lovato .

"We’ve been through so much together," the singer said of her fellow Disney Channel alums. "It was really, really great to spend time with them."

Demi Lovato is opening up about how that on-stage Camp Rock reunion with the Jonas Brothers happened, starting with how Joe reached out about being involved in night one of their Greetings From Your Hometown tour in New Jersey and why it was an instant "let's do this."