When your first single from Grease, the biggest movie musical of all time, is the chart-topping "You're the One That I Want," and it becomes the best-selling duet in pop music history - that's a tough act to follow. Almost 35 years later, John Travolta and Olivia Newton-John have combined their iconic voices for This Christmas, a newly recorded album featuring Christmas favorites with guest artists such as Barbara Streisand, Tony Bennett, and James Taylor!