The Voice – Season 6 Published June 2, 2014 at 900 × 600 in Gwen Stefani & Pharrell Williams Sing ‘Hollaback Girl’ During Surprise Performance – Video THE VOICE — “Live Show” Episode 619A — Pictured: (l-r) Gwen Stefani, Pharrell Williams — (Photo by: Trae Patton/NBC)