Dancing with the Stars' Derek Hough channeled the Halloween spirit with his girlfriend Hayley Erbert and fans couldn't believe it.MORE: Derek Hough and Hayley Erbert's new performance has fans in a frenzyThe judge shared a picture on his Instagram that featured him and Hayley in their Halloween costumes, dressed as Beauty and the Beast.He wore a full blue and white suit and she wore a fitted yellow ball gown to embody the characters.