Justin Timberlake, Jimmy Fallon are best friends who can't stop singing at Camp Winnipesaukee

You know a sketch is going to be good when it has Justin Timberlake, Jimmy Fallon AND music involved.

On Tuesday's episode of The Tonight Show, the host and musical guest teamed up for a humorous look into what they would've been like as young cabin mates at summer camp. 

Inside their cabin, the braces-faced and curly-haired duo had the urge to sing instead of going to bed.

Their song of choice? A hilariously horrible rendition of 4 Non Blondes' What's Up. 

But the fun came to an end when camp counselor Mr. Fletcher (Keegan-Michael Key) broke up the singing to tell them to "stop the ruckus" and go to sleep.

"It sounded like you guys were drowning in a lake," Key says in the sketch. "But you guys aren't drowning, are ya? You're clowning."

Later, a boy from a neighboring camp (Billy Crystal) joins in on the late-night concert to sing Gloria Estefan's Rhythm Is Gonna Get You with Timberlake and Fallon. 

Watch the full clip below.