Carrie Underwood brought legendary rocker Joan Jett to the stage to surprise the fans at the 2019 CMA Fest in Nashville in June, and while the country superstar was excited, she says Jett was actually a little bit apprehensive.

Jett took the stage during Underwood's set at Nissan Stadium in Music City on June 7 to join the "Southbound" singer in performing "I Hate Myself for Loving You," "Bad Reputation" and "I Love Rock 'n' Roll."

The live jam came about after Underwood decided to just invite Jett, whose music she has admired for a long time.

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"The stars just aligned. It was like, 'What if Joan Jett came to CMA Fest? Let's ask her!'" Underwood said (quote via the Boot). "So she's here. The coolness has arrived, and I'm hoping some of it rubs off on me."

“You can tell that she really wants to do a great job in this crowd," Underwood told assembled reporters backstage before their live collaboration. "I don’t want to say … it’s not like nervousness, it’s just wanting to do well, and then she’s like, ‘Because I know this isn’t my world and I just hope they know the songs.'"

Underwood was quick to assure Jett that she had nothing to worry about.

"I'm like, 'Are you kidding me?! Of course they know the songs!'" she exclaimed. Click on the fan-shot videos in this post to see how the crowd reacted to their unexpected jam.

Underwood was very familiar with Jett's music previously. Jett's "I Hate Myself for Loving You" provided the basic framework for "Waiting All Day for Sunday Night," which served as the theme song for NBC's Sunday Night Football from 2006-2016. Underwood performed the song from 2013-2016, taking over for Faith Hill, who sang the song from 2007 through 2012.

Underwood and Jett's joint performance is one of the highlights that will air as part of CMA Fest: The Music Event of Summer on Sunday night (Aug. 4) at 8PM ET on ABC.

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