Billie Eilish made a surprise appearance on stage with Green Day on Thursday to kick off one of two star-studded concerts in Los Angeles put together to raise funds for people affected by deadly wildfires in California this month.

The members of No Doubt -- Gwen Stefani, Tom Dumont, Tony Kanal and Adrian Young -- reunited at FireAid Thursday night and sang some of their biggest hits, including "Just a Girl," "Spiderwebs" and "Don't Speak."

A cavalcade of enormous rock and pop stars, old and new, will perform at an enormous benefit concert in Los Angeles, and streamed around the world.