Fans at Kelsea Ballerini's Los Angeles, Calif. Heartfirst Tour stop on Thursday night (Oct. 6) got a big surprise when Kenny Chesney popped up onstage for a live rendition of the two singers' No. 1 hit duet, "Half of My Hometown."

They weren't the only ones: While artists typically know in advance if they're planning to bring out guest performers, it seems that Ballerini was as surprised as the audience when Chesney walked out onstage. When she saw him, she was visibly shocked, and even appeared to mouth "what the f--k" in amazement, according to Country Now.

The pair then launched into a performance of their ballad, which comes off of Ballerini's self-titled 2020 album. They've performed it together a handful of times, beginning with the song's live debut at the ACM Awards in 2021.

After Thursday night's show, Ballerini revisited the jaw-dropping surprise on social media, posting a couple of photos of her duet with Chesney, plus one snapshot of her crouching down in one corner of the stage, obviously surprised to see him there. "Half of my hometown showed up in Los Angeles last....WHAT A SURPRISE I'M STILL LOSING IT?!?" she wrote on Twitter.

Ballerini's L.A. performance took place at the City's Greek Theatre; she's currently on the back half of her Heartfirst Tour, a 10-date trek that will conclude on Oct. 14 in Mashantucket, Conn.

Chesney's surprise appearance was not the first time a guest star made an appearance on Ballerini's Heartfirst Tour stage. During her Chicago date, Ballerini brought out Carly Pearce. The two singers are longtime friends, and Pearce -- along with Kelly Clarkson -- lends her voice to Ballerini's new Subject to Change album on one track, "You're Drunk, Go Home." Subject to Change came out in late September.

Kelsea Ballerini Tributes Shania Twain at ACM Honors

Kelsea Ballerini was on hand at the 2022 ACM Honors to celebrate Shania Twain, who took home the ACM Poet's Award. Ballerini recreated Twain's iconic music video for her 1999 hit, "Man, I Feel Like a Woman," on the Ryman Auditorium stage.

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