Chappell Roan Joins Charli XCX for First 'Boom Clap' in Brat Era

Chappell Roan surprised the Kia Forum crowd in Los Angeles on Saturday night, joining Charli XCX for a duet on "Boom Clap" — the first time Charli has performed her 2014 breakthrough single live during the Brat/Music, Fashion, Film era.

The cameo came mid-set on the Los Angeles stop of Charli XCX's Music, Fashion, Film Tour. Roan's condition for appearing, according to Charli, was that the song had to be this one.

"Every night on tour, I play an old song," Charli told the audience. "I asked a friend of mine if she would come and sing an old song of mine with me, and they said, 'The only way I'm doing it is if it's this song,' so you have her to thank."

Who else showed up?

Roan wasn't the only guest. Later in the set, Charli brought out PinkPantheress, who performed her own track "Stateside" for the Kia Forum audience.

One more surprise followed: the Dare arrived to help close things out on the Billie Eilish remix of "Guess," with cannons firing pairs of underwear into the crowd — a signature stunt from the song's live arrangement.

What does this change for the tour?

The guest pattern is now a fixture, not a one-off. Last weekend at the Austin City Limits Festival, Charli invited Tinashe onstage to perform "Melatonin" and "Nobody Wanna Dance Anymore" live for the first time.

The Music, Fashion, Film Tour continues Sunday night with its second of two shows at the Kia Forum. Expect the guest slot — and the guessing game around it — to stay part of the draw.