This is really funny! Ricky Gervais is usually game for a laugh, and his appearance on Jimmy Fallon's Tonight Show on Tuesday, Dec. 9, was no different.

But neither Fallon nor the audience could have imagined the trouble the former Golden Globes emcee could cause when given control of the show host's lips!

Totally cracking up, Gervais first acted out some facial features as Fallon's lips were morphed onto his (usually hirsute) chin. The English comic looked bizarrely young without his beard and Fallon dined out on the observation, making baby noises and sticking his tongue out like a child.

Ready to get his own back, Gervais' mouth (which made Fallon look rugged and rough around the edges thanks to his somewhat wonky teeth) then decided to let out some of Fallon's secrets.

"I'm Jimmy Fallon," Gervais said, speaking on the show hosts' behalf. "And I shave my balls."

Watch the hilarious segment above to see Fallon's reaction, and listen to the duo perform a Christmas carol with each other's lips in place!