Christmas came early for ’90s nostalgists and alternative rock radio fanatics over the weekend. Those who ventured out to the annual KROQ Almost Acoustic Christmas in Los Angeles were given a rare gift on Saturday night. During Bush’s set, the band vacated the stage while Gavin Rossdale went in on the guitar grind and gruff-guy vocals of their 1995 hit, “Glycerine.” But after a minute, a second voice is heard: Gwen Stefani had been waiting in the wings, and came out to deliver a surprise duet with her husband. The fan-shot footage above isn’t perfect, and the audio is at times overwhelmed with orgiastic screams, but the moment was sufficiently captured in all of its harmonically imperfect, ain’t-they-cute glory all the way down to the kiss at the end. While the two-day concert was celebrating its 23rd installment, the couple of the hour had their own anniversary to honor. Rossdale and Stefani actually met at the 1995 edition of KROQ Almost Acoustic Christmas. My, how the days go by.