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'America's Got Talent' winner Grace VanderWaal doesn't know who 'NSync is

Grace VanderWaal joined Jimmy Fallon on "The Tonight Show," where she gave another all-star performance and admitted she doesn't know who 'NSync is.
/ Source: TODAY

Recently crowned "America's Got Talent" season 11 winner and all-around adorable ukulele player Grace VanderWaal stopped by "The Tonight Show" yesterday to performed her original song "Clay," and play a hilarious singing-edition game of "chubby bunny" with host Jimmy Fallon.

The late-night talk show host, with a gigantic bowl of marshmallows on hand, explained to the 12-year-old folksy crooner that she'd have to guess the name of the song he was singing — with his mouth full of the fluffy confections.

In a nod to "AGT" judge Simon Cowell's comment that VanderWaal is the "next Taylor Swift," Fallon starts the challenge with one of the pop princess's most recognizable recent hits, "Shake It Off," from the album "1989."

After a few seconds, VanderWaal guesses correctly and even does a little shaking it off alongside the host. (She even received a sweet surprise from Swift herself after taking home the title).

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Simple enough so far, right?

Wrong.

Be warned, '90s kids: What you're about to hear may surprise you (and make you feel very, very old).

For his next number, Fallon pays homage to his longtime friend Justin Timberlake, and travels back to the golden days of our '90s boy band dreams, cleverly re-enacting the classic hand movements to 'NSync's (aka boy band royalty) timeless hit "Bye Bye Bye." Who could forget that epic puppet-string music video?

But VanderWaal is dumbfounded.

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Fallon repeats the hand motion a second time, but that only confuses her more.

"Talk, talk, talk? Down? High-low? Hello?" she guesses, amusing the crowd next to a frustrated Fallon.

"Bye Bye Bye," Fallon corrects, as he hilariously spits out the pile of marshmallows.

Unfortunately, that still doesn't spark any recognition from VanderWaal, who wasn't born until four years after the song was released in 2000 (so, can we really blame her?).

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"Bye Bye Bye — what?" VanderWaal asks, eliciting an uproar of laughter and shock from the crowd as a flabbergasted Fallon puts his face in his hands.

"I'm so old," laments Fallon.

"You'll listen to it. It's an oldie but a goodie," he jokes.

When the roles reverse, VanderWaal chooses the hits songs "Call Me, Maybe?" and "Hotline Bling," which Fallon guesses correctly (but not before throwing out Michael Jackson's "Thriller" — another oldie!).

Grace VanderWaal and Jimmy Fallon
The Tonight Show Starring Jimmy

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Later on in the show, the "I Don't Know My Name" singer performed her original song "Clay" on her trusty ukulele to cap off what has surely been an exhilarating week since she snagged the "AGT" crown.

We hope that after her appearance, VanderWaal went home to study up on some very important '90s boy bands. In the meantime, we'll be waiting to see what Fallon's BFF Justin Timberlake has to say about this.