"If you do a dance for me," Carrie sang to a fan. "You're gonna get those cowboy boots for free. So start moving and shake your derrière."
Carrie Underwood is giving some lucky fans quite the surprise -- and a pair of new boots!
In the latest edition of "Jimmy Kimmel Live's" segment "Undercover Sing" Tuesday night, the country star, who is hosting the 2019 CMA Awards this Thursday, went incognito to surprise customers in a Nashville boot shop with a personal serenade.
As hidden cameras filmed the shoppers, Underwood patiently waited in the back of the store for the perfect moment to pop out. For each fan or group of fans, the Grammy winner sang to the tune of her song "Before He Cheats" and customized the lyrics to fit each shopper.
First up were three ladies, one of whom had dark purple hair. After the sales associate asked where the women were from, Underwood, watching the security footage, began to sing over the loudspeaker.
"Right now, we got three ladies who wanna buy some cute boots to go line dancing," she sang. "Right now, one lady has purple hair. She's the punk rock one, gonna get some boots now."
"These girls are coming from Virginia," Underwood continued. "Virginia is for lovers, lovers of boots. This lady is laughing because she knows that I'm singing about her and her boots."
As the women seemed to start to realize what was going on, Underwood came out for the surprise.
"No way!" one of the ladies exclaimed. "Is it really you?!"
Underwood took things to the next level for a second customer, a man named John. The "Cry Pretty" singer informed John, by song, that if he danced she would purchase his boots for him.
"John is holding onto his shoes," Underwood began. "If he doesn't get boots, he'll have the blues. Take it from me, Carrie Underwood."
"If you do a dance for me," she continued. "You're gonna get those cowboy boots for free. So start moving and shake your derrière. Dance again and don't you stop. In your cute blue sweater top. I promise those boots will be on me."
John, as instructed, shook his booty to get those free shoes.
See more priceless reactions to Underwood's surprise in the full clip, above.