If you're not a John Kransinski fan ... you will be after watching this!

On Tuesday, "The Office" star appeared on "The Late Night with Jimmy Fallon," where John and Jimmy shared one amazing lip-sync battle.

The duo did their best singing impressions, belting out everything from Katy Perry's "Teenage Dream" to Boys II Men's "I'll Make Love To You." Check out the hilarious clip above!

How great is John's rendition of the Boys II Men ballad at the end? We think Kransinski definitely won the lip sync-off.

Who do you think fake sang it better? Sound off below!

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