Two concerts collectively referred to as FireAid kicked off at the Kia Forum and the Intuit Dome in the city of Inglewood in Los Angeles County to support relief efforts in the wake of the deadly wildfires that ignited earlier this month in the LA area, claiming 29 lives and causing billions of dollars in damage.

Audiences tuning into the FireAid benefit concert for Los Angeles on Thursday night (Jan. 30) were surprised with an early treat when pop superstar Billie Eilish made a surprise appearance alongside Billie Joe Armstrong and the rest of Green Day for a stirring opening performance.

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.