Watch Kelly Clarkson and Dolly Parton Flawlessly Harmonize Impromptu 'I Will Always Love You' Duet

Dolly Parton and Kelly Clarkson know how to give fans what they want!

During an appearance on The Kelly Clarkson Show on Thursday, the "9 to 5" singer revealed the story behind how she heard Whitney Houston's iconic cover version of "I Will Always Love You" for the first time.

Parton, 76, recounted how Kevin Costner called her to ask if he could use the song — originally written by Parton — for the 1992 film The Bodyguard, and she said yes. Then, she told Clarkson, "I didn't hear anything else about it. I didn't know if they had it, I didn't know if they had done it."

She continued, "I was just driving along, I had the radio on and I heard this..," she recalled. "When I heard the first 'If I...' I just freaked out. I had to pull over to the side because I honestly thought that I was gonna wreck. It was the most overwhelming feeling and you know how great that was."

Weiss Eubanks/NBCUniversal via Getty (2) Dolly Parton and Kelly Clarkson

RELATED: Kelly Clarkson Honors Dolly Parton with Stunning 'I Will Always Love You' Performance at ACM Awards

She then went on the praise the 40-year-old "Since You've Been Gone" singer for her performance of the track at the ACM awards in March — which she did as a tribute to Parton.

"I've been meaning to tell you, that whole crowd, Whitney, she would've been so proud of you. It was incredible," the "Jolene" singer told Clarkson.

Then, Clarkson turned to the audience members, who were requesting they sing the legendary song on the spot — and she declined. Instead, Parton insisted she would sing it while Clarkson harmonizes.

Weiss Eubanks/NBCUniversal via Getty

And just like that, the two icons sang a brief portion of "I Will Always Love You" together, and the audience cheered them on.

"Your breaks in your voice are so magical. You're like a magical fairy human," Clarkson told Parton.

Elsewhere during the episode, the two artists sang a cover version of "9 to 5" for the series' daily Kellyoke segment. The performance came three months after they teamed up to record a duet version of the song for the documentary Still Working 9 to 5, which premiered on Sept. 16.

RELATED: Dolly Parton Says 'Nobody Sings Like Kelly Clarkson' as They Unveil Newly Reimagined '9 to 5' Duet

"Nobody sings like Kelly Clarkson. She makes any song come alive," said Parton in a press release about the song at the time. "I love her voice on '9 to 5,' and I am so proud I got to sing with her on it. I'm equally as proud of the wonderful arrangement and production by Shane McAnally."

In a press statement, Clarkson expressed immense admiration for Parton as well. "I am so honored that Dolly asked me to reimagine this iconic song, '9 to 5,' with her!" wrote the TV host. "She is so talented, an inspiration to all women, and one of the sweetest people you will ever meet!"

Clarkson continued, "I hope y'all like what we did, but even if you don't, remember I got to sing a duet with the magical Dolly Parton, and now have bragging rights til the end of time!"