ABC/Paula LoboHalsey and Avril Lavigne took the stage for an impromptu duet this weekend at Halsey’s annual Halloween bash.

Halsey, dressed as goth rocker Marilyn Manson, joined Avril, dressed as 1980s Madonna, to sing Avril’s 2007 hit “Girlfriend.” The crowd–– and later, Twitter — went nuts over the collab.

“I can’t believe I got to witness Halsey and Avril Lavigne singing ‘Girlfriend’ in the year 2019 !!!! ICONIC,” one fan tweeted.

While another wrote, “THIS IS EVERYTHING.”

Halsey also debuted her budding romance with American Horror Story actor Evan Peters at her Halloween party Friday. Then on Saturday, they attended American Horror Story‘s 100th Episode Celebration dressed as Sonny and Cher.

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