Gwen Stefani made fans go bananas at the opening night (Aug. 3) of the Watershed Music and Camping Festival in Washington.
Stefani's unexpected pop-in arrived during her boyfriend Blake Shelton's Saturday headlining set at the three-day event.
While on stage, Stefani led the crowd in an energetic sing-along of her 2005 hit "Hollaback Girl." Watch the ecstatic Watershed crowd belt out the song's famous line, "Let me hear you say, this shit is bananas, B-A-N-A-N-A-S!" in the clip below.