Grammy-nominated 'Brat' track at Eilish's Kia Forum concert 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.

Billie Eilish surprised fans with Charli XCX on Tuesday to deliver the live debut of their "Guess" (Remix) in Los Angeles at the Kia Forum. On the third of five nights at the arena for Eilish, the pair took the “Brat”-green lit stage to sing their Grammy-nominated high-energy track.

Billie Eilish welcomed Charli XCX onstage at the Kia Forum in Los Angeles last night for a surprise performance of their collaborative hit track "Guess." The energetic track comes off Brat and It's Completely Different but Also Still Brat,

After teaming up on Brat and It’s Completely Different but Also Still Brat, Billie Eilish and Charli XCX teamed up to give their duet, “ Guess ” (Remix), it’s live debut at the Los Angeles Kia Forum last night.

Billie Eilish brought Charli XCX on stage to perform the Guess remix during her recent show in Los Angeles. The Bad Guy singer thrilled fans on Tuesday night when she brought the British hitmaker on stage for a surprise live performance of their Grammy-nominated collaboration.