During the pre-recorded segment, the singer hid in a back room of the store and sang to customers, who were left looking around in disbelief at what they were hearing.
As different groups walked in, the "Cry Pretty" hitmaker sang over the loudspeaker to the tune of her massive hit "Before He Cheats" - except with different lyrics.
With one customer, named John, the country music superstar encouraged him to dance in order to get a free pair of boots, as she sang, "John is holding on to his shoes / If he doesn't get boots, he'll have the blues."
"Take it from me, Carrie Underwood / If you do a dance for me, you're gonna get those cowboy boots for free / So start moving, and shake your derriere."
While the audience cheered as John began to move, Carrie continued singing until he gave a satisfactory performance to take home the footwear.
When the next customer, named Dan, entered the store looking for ostrich boots, the "American Idol" winner serenaded him with facts about the physiology and ancestry of the large birds.
"Right now, Dan from Virginia is looking for some boots made out of ostrich... Did you know chickens and ostriches are the closest modern relatives to Tyrannosaurus rex?" she sang. Dan replied, "I don't think that's true."
"I bet you didn't / Did you know ... ostriches they have three stomachs," Carrie kept singing, as Dan pulled out his phone and chimed, "I'm looking all this stuff up."