Viewers of the 2017 ACM Awards on Sunday night (April 2) saw T-Mobile Arena go absolutely crazy during Florida Georgia Line's "God, Your Mama and Me" / "Everybody (Backstreet's Back)" mashup with the Backstreet Boys. The country duo and their boy band buds basically turned a room of country superstars into a crowd of screaming fans -- including Tim McGraw!

When Tyler Hubbard and Brian Kelley invited Nick Carter, Howie Dorough, Brian Littrell, AJ McLean and Kevin Richardson onstage to perform during the 52nd annual ACMs, it was a sure bet that they'd together sing their recent hit “God, Your Mama and Me," but the all-out dance party that broke out was a total surprise. With the first few bars of BSB's 1997 hit "Everybody (Backstreet's Back)," the crowd was on its feet: Carrie Underwood was dancing with Keith Urban and his wife Nicole Kidman, Brittany Kerr was singing along next to her husband, Jason Aldean, and McGraw completely lost it when the whole entourage -- Kelley and Hubbard included -- launched into BSB's original dance moves.

After the awards show, FGL shared the clip of McGraw pointing at them in pure astonishment as they nailed BSB's "Everybody" routine, which Hubbard reveals that he and Kelley only learned that day.

"We had our first dance lesson today!" Hubbard told Entertainment Tonight right after their performance. "Nick Carter! Not mad about that."

Although FGL were too focused on getting the right moves during their performance to check out the crowd, they could definitely tell that everyone was having a good time. However, it wasn't until after the performance (and after they ran into McGraw backstage) that the guys got to see the clip of him freaking out.

"Somebody just showed us a clip, and we actually were just hanging with him," Kelley said. "We saw the video, and he's pointing. [McGraw told me], 'I was pointing at you 'cause you were nailing all the moves, you got ‘em!' I was like, 'I appreciate that, Tim.'"

This summer, Florida Georgia Line will bring the Backstreet Boys out on the road for three stadium shows during their 2017 Smooth Tour. Here's hoping that they bring back those dance moves, too!

See More Photos From the 2017 ACM Awards

How Well Do You Know the ACM Awards?