Two of the evening top-billed acts, Billie Eilish and Green Day, decided to sneak in an onstage duet. As the band geared up to play their beloved 21st Century Breakdown track “Last Night On Earth,” Eilish shocked viewers by picking up a microphone ahead of her set.

Green Day opened up the benefit concert and were quickly joined by Eilish for a performance of the band’s “Last Night on Earth” from their 2009 album “21st Century Breakdown.” Eilish departed the stage after the duet and Green Day continued with “Still Breathing” and “When I Come Around.”