Billie Eilish Makes Surprise Appearance with Lana Del Rey at Coachella

Billie Eilish gave herself -- and the crowd -- a real treat at Coachella Friday night ... turning up on stage as a special guest to perform with her idol Lana Del Rey.

The iconic pairing came as a surprise to the packed audience on weekend 1 of the 23rd annual festival in Indio, California. But, for Billie, it was everything she could ever hope for given that Lana has been such a major influence on her music.

Bille suddenly emerged from backstage and launched straight into her tune, "Ocean Eyes," with an assist from Lana. Then the stars did another duet, singing Lana's song, “Video Games."

Near the end, Billie spiced it up a bit, shouting her love for Lana in a defiant tone, “Get the f*** out of my face!” Lana then addressed the audience, referring to Billie as "the voice of a generation!”

Although the entertainers never linked up to make music before Friday, Billie told Interview magazine last year that Lana paved the way "for everyone," changing the way other artists look and sound.

Meanwhile, fans of Taylor Swift thought the pop superstar would join Lana onstage because of their previous work together, but no such collab took place.