This should cheer you right up! The cast of "The Tonight Show."

These "A Cappella" videos are becoming staples of Fallon's "Tonight Show," and this holiday version of McCartney's classic (complete with animated characters) is a welcome addition.

Check it out:Matthew McConaughey stars in "Sing" as the voice of koala Buster Moon, who produces a greatest singing competition to try and save his theater. McC was a main guest of last night's show, doing some Kid Theater (another Fallon classic) and sharing his holiday plans -- including a family trip to Brazil."Sing" opens Dec. 21, aka today, and McConaughey's other movie, "Gold," opens Christmas Day.

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