Charli xcx Joins Billie Eilish for Live Debut of Their ‘Guess’ Remix at L.A. Show

On Tuesday, Dec. 17, the pair performed the Grammy-nominated 'Brat' track at Eilish's Kia Forum concert

 Christopher Polk/Billboard/Getty  Charli xcx and Billie Eilish in December 2024

Christopher Polk/Billboard/Getty

Charli xcx and Billie Eilish in December 2024

Billie Eilish's latest concert got the Brat treatment.

On Tuesday, Dec. 17, Charli xcx made a surprise appearance at the "Birds of a Feather" hitmaker's Los Angeles concert at the Kia Forum.

Just one day prior to Eilish's 23rd birthday, the pair celebrated with the live debut of their "Guess" remix from the "Apple" musician's acclaimed album Brat and It’s the Same but There’s Three More Songs So It’s Not.

Related: Billie Eilish Bulldozes Her Way into Charli xcx's Underwear Party in Music Video for 'Guess' Remix: Watch

During the set, the pair were engulfed in green lasers as they bounced around the stage and amped up the audience.

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While Charli, 32, and Eilish, 23, danced, the crowd chanted the lyrics: “Don’t have to guess the color of your underwear/ Already know what you’ve got goin’ on down there/ It’s that lacy black pair with the little bows/ The ones I picked out for you in Tokyo,”

The "360" musician also shared her excitement about their set on Instagram with a video of their set and a birthday tribute.

"love u billieeeeee and hbd!!! <3," Charli wrote on the social media platform.

In August, Charli and Eilish released their "Guess" remix with an accompanying music video.

In the visual, directed by Aiden Zamiri, Charli is at a house party with people drinking and dancing as they begin to strip down to their undergarments. Then, Eilish breaks into the house with a bulldozer to sing her section of the track.

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Then, they end up outside and surrounded by industrial buildings when it begins to rain bras and underwear. (According to a press release, all bras and underwear used in the music video were donated to I Support the Girls.)

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Alberto Rodriguez/Variety via Getty; Alberto Rodriguez/Variety via Getty Billie Eilish in March 2024; Charli xcx in March 2024

Alberto Rodriguez/Variety via Getty; Alberto Rodriguez/Variety via Getty

Billie Eilish in March 2024; Charli xcx in March 2024

Related: Charli xcx, Billie Eilish Donate Unused Underwear from 'Guess' Remix Music Video to Survivors of Domestic Violence

During the song, Eilish adds a clever — and flirtatious — nod in the chorus.

"I wanna try it, bite it, lick it, spit it/Pull it to the side and get all up in it/Kiss it, bite it, can I fit it?/Charli likes boys, but she knows I'd hit it/Charli, call me if you're with it," Eilish, who's been open about her bisexuality, sings on the track.

"Guess" was originally released as a part of Brat and it's the same but there's three more songs so it's not in June.

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