The phrase comes from the Saturday Night Live sketch first aired in April 2000, written around a fictional recording session for Blue Öyster Cult's Don't Fear The Reaper. Christopher Walken plays producer Bruce Dickinson, who repeatedly insists the track needs more cowbell, while Will Ferrell plays Gene Frenkle banging the instrument with total commitment. The sketch quickly moved beyond the show into quotes, shirts, and early internet soundboards. Its simple, repeatable demand made it perfect for remixes and reaction clips, and it remains one of SNL's most quoted moments.