When Little Big Town played their hit 'Pontoon' at the Grand Old Opry on Friday night (Oct. 4), they had an extra-special surprise guest join them onstage -- the one and only Reba McEntire. But, she wasn't just there to sing: She extended a very special invitation to the country quartet.

Karen Fairchild, Kimberly Schlapman, Phillip Sweet and Jimi Westbrook were immersed in hitting their perfect harmonies during the performance when McEntire strode onstage, adding her distinctive vocals to the mix.

Obviously, they were more than delighted to see the county star, who quipped, "I'll do anything to get on the stage with y'all." Then, McEntire got down to business.

"Alright, I've got somethin' to tell ya," she announced, as Fairchild and Schlapman moved in close, their arms around the fiery redhead. "I know the Grand Ole Opry is very important to y'all," she said, mentioning that it was the first place LBT played together in 1999. "Little Big Town, would y'all like to be a member of the Grand Ole Opry?"

The two women of the band doubled over in disbelief while their bandmates whooped, hollered and looked on in utter shock.

"Oh my gosh, this is a dream, this is a dream," gasped Fairchild.

While LBT caught its collective breath, Schlapman got another surprise -- one that moved her (and probably all viewers!) to tears: Her parents were backstage, witnessing all of it. Of course, the 'Day Drinking' hitmakers said 'yes' to the opportunity, and they will be officially inducted by Vince Gill on Oct. 17. Tickets are available on the Opry's website.

LBT are poised to release 'Pain Killer,' the band's sixth studio album, on Oct. 21, with a tour that kicks off Nov. 11 and features opening guests Brett Eldredge and the Brothers Osborne.