Demi Lovato looked flawless. Fetty Wap, recovering from a recent motorcycle accident, was all smiles perched on a gold throne. Selena Gomez joined Russian EDM savant Zedd for a surprise duet. This year’s Z100 Jingle Ball at Madison Square Garden was a total smash onstage, but the pop all-stars were even more festive behind the scenes. In between exchanging hugs and holiday cheer, Vulture snagged a few minutes of their time backstage to snap some pics and get the intel on their preshow rituals.