What makes Happiness by Red Velvet notable?

'Happiness' debuted at number one on the Gaon Digital Chart, showcasing its immediate commercial success. The song's bright concept helped define Red Velvet's duality of vibrant and sophisticated themes in subsequent releases, making it a pivotal moment in their career. Released on August 4, 2014, 'Happiness' was Red Velvet's debut single, marking their introduction to the K-pop scene. At this time, the group was establishing their identity within SM Entertainment, transitioning from pre-debut promotions and showcasing a fresh sound that combined various musical influences.