One Direction, Jimmy Fallon One Direction, Jimmy Fallon

Jimmy Fallon's classroom instruments performances have become a beloved staple of The Tonight Show, but the host stepped his game up when he invited One Direction to don their gay apparel and join him in a carol Monday.

Dressed in their Christmas best (ugly sweaters, that is), One Direction, Fallon and The Roots rocked out to "Santa Claus Is Coming to Town."

Remember celebrities we lost this year

If the video below only whets your appetite for more 1D, don't worry. The boys' NBC Christmas special airs Tuesday at 8/7c.