The powerful vocalist belts out an Aretha Franklin cover and her own hit, "Fighter."
A hat, wig and sunglasses couldn't cover up Aguilera's most recognizable feature -- her voice. We can't imagine onlookers weren't immediately suspicious when they began gathering around the singer belting out Aretha Franklin's hit "Think."
After finishing to a booming applause from a very appreciative audience, Fallon revealed their identities to the New Yorkers, who cheered even louder when they got confirmation it was indeed Aguilera.
Even more cameras came out when Aguilera and Fallon's band wrapped up by performing one of her biggest hits, "Fighter."
But don't worry, she went back to the "Tonight Show" studio to do a proper performance, too.
Enjoy her crushing her latest hit, "Fall in Line" -- sadly without Demi Lovato -- from her new album, "Liberation," below.