It was no 'History of Rap,' but whenever you get Jimmy Fallon and Justin Timberlake together, you know it'll be great. And so it was on Tuesday night when JT made a surprise appearance during a Fallon sketch.

Playing younger and much nerdier versions of themselves in a supposed flashback, the guys were roommates at camp who duet on their favorite "new" song: Hootie and the Blowfish‘s 'Only Want to Be With You.' Of course they're interrupted by a killjoy camp counselor a couple times, but that doesn't stop them from belting it out anyway.

Bonus points for the fake braces they both rock and their inability to keep a straight face -- especially during a silly nut allergy joke.

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