Derek Hough treated DWTS fans to a special night on Monday.The beloved host returned to the floor to perform a sexy routine with girlfriend Hayley Erbert.According to CNN, it was Hough's first time dancing on the show since 2017.The happy couple danced a paso doble to Taalbi Brothers' "Uccen."Hough and Erbert, who have been dating for five years, say they have grown even closer during the pandemic."We grew as a couple tremendously," Hough recently said during an appearance on "The Ellen DeGeneres Show."