Country music group Little Big Town got a big surprise during their performance at the Grand Ole Opry over the weekend.

The group’s members, Karen Fairchild, Kimberly Schlapman, Jimi Westbrook and Phillip Sweet, were performing their hit song Pontoon on the stage when they heard a fifth voice join in for the chorus.

“I thought, who’s singing?” Westbrook later recalled backstage. “Who’s singing an ad lib that we didn’t talk about?” Westbrook’s wife and fellow group member Fairchild also recalled after their performance.

They soon got their answer when Country Music Hall of Famer Reba McEntire walked on stage to present the ultimate surprise … an invitation to join the Grand Ole Opry.

The group was obviously shocked and at a loss for words. According to People, “Kimberly Schlapman buried her face in her hands, Fairchild slumped onto McEntire’s shoulder, Phillip Sweet slapped his forehead, and Westbrook did a backbend worthy of an Olympic gymnast.”

We think October is going to be our favorite month of the year! @opry Invite 10.3.14 & #PainKiller out 10.21.14 pic.twitter.com/4Rox58jkBw

— Little Big Town (@littlebigtown) October 5, 2014

The official induction will take place on Friday, October 17. “People ask, ‘How do you know when you’ve made it?’ Now I know,” Westbrook said.

.@reba there is absolutely no way last night could have been more perfect. Thank you from the bottom of our hearts!

— Little Big Town (@littlebigtown) October 4, 2014

“This is like the pinnacle,” Fairchild added. “This is forever. Here, in the ladies’ dressing room tonight, I was looking at [photos of] Emmylou [Harris] and Dolly [Parton] and Patsy [Cline], and now we’re going to be [in the club].”