Gwen Stefani and Gavin Rossdale duet on 'Glycerine': Watch the video now

At KROQ's Almost Acoustic Christmas this weekend, Bush frontman Gavin Rossdale performed an (extremely) rare duet with his wife, No Doubt's Gwen Stefani, who he actually met at KROQ's Almost Acoustic Christmas 17 years ago.

Fans were shocked as Rossdale, alone with his guitar, began to sing "Glycerine," and then Stefani, unnannounced, walked on stage to join in the second verse. Rolling Stone reports that the crowd went wild.

"She actually asked me about this and I was so surprised, I didn't say anything for two days," Rossdale tells the mag. "She said, 'Maybe we should do a song together.' And I couldn't answer her."

They also considered performing his song "The Afterlife," which is her favorite, but settled on "Glycerine."

"I thought it would be so powerful, the two of us on stage like that, that's what we went for," he says. Rossdale, who has just been touring for two years, is looking forward to some family time over the holidays. "This is the culmination of two years of work, and then to finish it off playing here, in this venue, this full circle thing, it was an incredible night."