What's the most obscure thing on Demi Lovato's tour rider? How about the word Nick Jonas overuses? Billboard put the pop stars and co-headlining tourmates' knowledge of each other to the test during a break from their recent cover shoot.
So, how did they do? Let's just say Demi has to clarify, "We're best friends, I promise." Check out the exclusive video above and find out Demi's go-to karaoke song, Nick's favorite singer and watch the two rap Eminem for a hot second. Then read this week's Billboard cover story, where the longtime pals talk overcoming their own personal obstacles, politics and whether they'd ever want to be college dorm mates.