'Tis the season to be jolly, and Reese Witherspoon was exactly that when she appeared on Jimmy Fallon's Tonight Show on Tuesday, Dec. 2, and got into the festive spirit with a bit of Christmas caroling!

"That sounds great," said an excited Witherspoon when Fallon suggested they partake in a festive sing-along. "I love Christmas carols." But, as with all things related to Fallon, it wasn’t as simple as it sounded. While the tunes were traditional, the show host had switched up the lyrics to the well-known songs, and the results were pretty funny!

"Do I have to go first?" asked Witherspoon, who looked seasonally stylish in a bright red dress, but sounded a little nervous about going solo.

Feeling gentlemanly, Fallon took the lead — singing a bizarre song about sniffing old men to the familiar tune of “Jingle Bells”. 

It was all a bit confusing for Witherspoon, 38, who struggled to remember the tune to “Silent Night” when faced with her bizarre lyrics. But it was the pair’s duet finale of “Deck the Halls” (or should it be “Squeeze the Cheese”?) which really brought the house down.

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Watch the whole segment in the link above and check out Reese's nifty vocal work!