Jimmy Fallon opened his "Saturday Night Live" monologue by singing "Joy To The World" while doing impressions of David Bowie, Bob Dylan, and Paul McCartney.

But Fallon was in for a surprise when McCartney actually walked onto the stage to join him in singing "Have Yourself A Merry Little Christmas."

When Fallon told McCartney he thought he couldn't make it because of traffic, the Beatle said he just hopped on a Citi Bike. Watch the entire opening monologue below:

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