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.

The "Birds of a Feather" singer hit the stage in coveted Air Jordan sneakers at her Los Angeles concert Tuesday night.

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,