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

Billie Eilish, Charli XCX at the Billie Eilish “Hit Me Hard and Soft” Tour at Kia Forum on December 17, 2024 in Inglewood, California.

Christopher Polk/Billboard/Getty

Billie Eilish’slatest concert got theBrattreatment.

On Tuesday, Dec. 17,Charli xcxmade 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" remixfrom the “Apple” musician’s acclaimed albumBrat and It’s the Same but There’s Three More Songs So It’s Not.

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

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 seton Instagramwith 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 accompanyingmusic video.

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

Billie Eilish at the 96th Annual Oscars held at Ovation Hollywood on March 10, 2024 in Los Angeles, California; Charli XCX at Vanity Fair and Instagram&rsquo;s Vanities: A Night for Young Hollywood held at Bar Marmont on March 6, 2024 in Los Angeles, California.

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

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’sbeen open about her bisexuality, sings on the track.

“Guess” was originally released as a part ofBrat and it’s the same but there’s three more songs so it’s notin June.

source: people.com