Way back before it became super annoying, Jimmy Fallon, the Roots, and Carly Rae Jepsen performed her summer mega-hit "Call Me Maybe" on a bunch of children's instruments and it was SO GOOD. Now JF and the band picks up their tiny xylophones again along with Mariah Carey to do a SO GOOD version of "All I Want for Christmas is You." Expect a huge smile, some comforting chills, and a kid choir THAT IS THE BEST. Check it out for the mood elevator you need today.