Plot: Comedian HOWIE MANDEL takes over as guest host and welcomes his friend MICHAEL BUBLÉ! The multiple-Grammy winner will chat about his family, being dubbed the “King of Christmas,” and divulge about the prank Howie pulled on him! A cappella superstars PENTATONIX will then take the stage to perform “I Just Called to Say I Love You” from their holiday album, “Evergreen. ” And you’ll want to hear the inspiring story from fourth grade teacher K