Halsey’s annual Halloween party got a big dose of Avril Lavigne this year.

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The bash, held Friday night in Los Angeles, featured a performance by Lavigne of her hit “Girlfriend”, with Halsey herself joining in.

People in attendance shared clips of the duo singing together on social media.

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The theme of the party this year was 1960s, ’70s, ’80s and ’90s rockstars, with Halsey dressing as Marilyn Manson and Lavigne going as ’80s-era Madonna.