They're currently preparing to go on tour together in June, but the kids at CHLA got an early preview of the show.
"It helps the kids feel special. When they're in the hospital so much, they think they're left out from a lot of normal things, whether it's school, seeing their friends," said Child Life Specialist, Lisa Cies.
Demi and Nick sang some of their latest jams, including "Confident" and "Jealous."
They also made time for photos and autographs.
Erin Shields, another Child Life Specialist at CHLA, said, "When they walked in, their faces...really lit up. It's really great when we're able to have those moments."