Last night on Late Night, Mariah Carey crooned her signature "All I Want for Christmas is You" to the warring cries of Jimmy Fallon and The Roots. Plus: Matt Damon considers Promised Land co-star John Krasinski the contemporary George Clooney. Per David Letterman, however, Clooney's "a boob" so that's not really a compliment. Also, Martin Freeman displayed the "emotional range" of his Lego Bilbo Baggins. Watch our compilation to see what you missed.