Green Day’s Billie Joe Armstrong on ‘Good Morning America.’ (ABC/Paula Lobo) Dua Lipa performs during the Radical Optimism Tour at Scotiabank Arena on September 01, 2025 in Toronto, Ontario. (Kevin Mazur/Getty Images for ABA)

Now that September’s ended and Billie Joe Armstrong is wide awake, the Green Day frontman made a surprise appearance at Dua Lipa‘s concert in San Francisco on Sunday.

During her ongoing tour, the pop star has been inviting up or covering artists related to the city she’s playing. In introducing Armstrong, who famously is from the Bay Area, Lipa told the crowd, “Immediately when I thought about San Francisco, and I thought about all the incredible music that has come out of here, I thought about one band in particular that would be perfect.”

“I love this band for so many different reasons,” Lipa continued. “I love it because of the rawness, the authenticity, the message behind it, the space that it holds for people who feel sometimes they might not belong. I loved listening to this album in particular when I was little, I would put the CD in the Walkman and just kind of sing my heart out.”

Armstrong then took the stage and joined Lipa for a rendition of the American Idiot single “Wake Me Up When September Ends.”

Green Day, meanwhile, recently wrapped their world tour supporting the band’s latest album, 2024’s Saviors. Their next release is a 25th anniversary reissue of their 2000 album, Warning, due out Nov. 14.