Billie Eilish joined Green Day on 'Last Night on Earth' to kick off the FireAid concerts in Los Angeles to benefit wildfire relief in the city.

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.

"California, Los Angeles, Altadena, the Palisades - we are in this together," Green Day's frontman Billie Joe Armstrong screamed to a sold-out crowd at L.A.'s Kia Forum on Thursday for the FireAid wildfire benefit concert.

Kelly Clarkson performed Billie Eilish's hit "Birds of a Feather" for the Kellyoke segment of her NBC talk show on Jan. 29. The song earned three nominations for the upcoming 2025 Grammy Awards, set to go down in Los Angeles on Feb.

The first of two concerts collectively being referred to as FireAid kicked off at the Kia Forum in the Los Angeles city of Inglewood, 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.

FireAid, featuring Billie Eilish, Lady Gaga, Sting, Red Hot Chili Peppers and others in a fundraiser for Los Angeles-area wildfire relief efforts, is the latest event to combine music and philanthropy.

Hans Zimmer's work will be brought to the live stage and feature a star-studded lineup that includes Billie Eilish, Timothée Chalamet, and Zendaya.

The FireAid benefit was fueled by some of music’s best performers to raise money for Los Angeles-area wildfire relief efforts.

Olivia Rodrigo and Billie Eilish led a roster of stars who brought the down house at Thursday's FireAid benefit concert in Los Angeles.

The FireAid benefit was fueled by some of music’s best performers to raise money for Los Angeles-area wildfire relief efforts.

In the past few weeks, people have been planning many, many benefits for the victims of the recent Los Angeles wildfires. The biggest of those shows went down last night: FireAid, a gigantic all-star spectacular that took over both the Intuit Dome and the Kia Forum.