TV Sing cast covers 'Wonderful Christmastime' with Jimmy Fallon, Paul McCartney The Christmas classic gets an acapella makeover, with a little help from the original maestro himself By Christian Holub Christian Holub Christian Holub is a writer covering comics and other geeky pop culture. He's still mad about 'Firefly' getting canceled. EW's editorial guidelines Published on December 21, 2016 07:45AM EST Photo: NBC Sing is a new film that features animated animal characters covering iconic pop songs. But with the film coming out so close to Christmas, Jimmy Fallon decided to apply the film’s approach to holiday tunes when the cast (stacked with celebrities like Matthew McConaughey and Scarlett Johansson) stopped by The Tonight Show on Tuesday night. Together, the group pulled off an acapella cover of Paul McCartney’s holiday classic “Wonderful Christmastime.” The Roots helped out, as always, but provided backing vocals rather than a backing beat. The biggest surprise, though, was McCartney himself, who joined in to help while the Sing cast switched back and forth between their real faces and the visages of their animal characters. Watch the clip below.