All the stars love Paramore. The Nashville emo greats opened some of Taylor Swift’s stadium shows earlier this year, and they’re about to rejoin Swift for the European leg of her Eras tour. Paramore leader Hayley Williams also just showed up on Speak Now (Taylor’s Version). At Bonnaroo last month, Williams joined the Foo Fighters onstage. Paramore are in the midst of their own arena tour right now, and they brought out a visibly starstruck Lil Uzi Vert to do “Misery Business” with them at Madison Square Garden a couple of months ago. And then there’s Billie Eilish.

Billie Eilish’s Paramore fandom is well-documented, and it’s not exactly surprising. When Eilish headlined Coachella last year, she brought Hayley Williams to the stage, and the two of them sang “Misery Business” and “Happier Than Ever” together. Last night, those roles were flipped around. Paramore played the Kia Forum just outside Los Angeles, Billie Eilish’s hometown, and Eilish joined the band onstage.

Paramore kicked off last night’s encore with their 2009 song “All I Wanted.” Midway through, Hayley Williams said, “Please welcome our friend Billie Eilish.” A visibly elated Eilish — who looked less like a glamorous pop star and more like an average circa-2009 Paramore fan — bounded onstage and sang the rest of the song with the band. Eilish and Williams both seemed to be having the time of their lives up there. Watch some fan-made videos below.

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