Pentatonix's holiday special was full of star-studded performances. In addition to performing a chilling duet with Kelly Clarkson, the a cappella group was also joined by '90s boy band, Backstreet Boys, for a stripped down rendition of "Winter Wonderland." The groups were in perfect harmony as they sang the holiday tune at Planet Hollywood, where BSB is currently performing their Las Vegas residency. While we have plenty of new BSB music to look forward to in the new year, this performance really has us wanting a full-length BSB Christmas album.
Image Source: NBC