Rolling Stones frontman Mick Jagger may have won Halloween with a costume portrayal of Pennywise from the movie It. Jagger donned the mask of the frightening clown at Rita Ora's London Halloween party. The 75-year-old had people guessing as to who was behind the mask. As for the host of the party, Ora came dressed as Cher's character Alexandra from The Witches of Eastwick. Rihanna also made an appearance at the Halloween bash. She covered her face in pink skull makeup. Check out Mick Jagger's costume below on the left!