"Dancing" pro Julianne Hough surprised the world Tuesday night by making her stunning dance-floor return.

Boogying to "Great Balls of Fire," Julianne's brother Derek Hough raised the lid on a piano, only for Julianne to pop out from behind it! The two danced up a storm to the crowd's delight.

Julianne, who underwent surgery to treat endometriosis, appeared to be in top form. Minutes before making her surprise return, she gave a backstage interview saying she was eager to come back!