In a television first, The Greatest Showman aired a live movie trailer during Fox’s telecast of A Christmas Story Live. The live two and a half minute trailer for Michael Gracey’s movie musical based on the life of P.T. Barnum featured the film’s stars Hugh Jackman, Zac Efron, Zendaya, and Keala Settle performing the high-energy number “Come Alive” alongside an army of 150 dancers on the stages at the Warner Bros Studios in Burbank. Academy Award-winning songwriters Benj…