"Happiness" (행복) is the debut digital single of Red Velvet. It was released on August 4, 2014.
- The music video was initially released on August 1, but then re-released on August 4, 2014 due to the controversial imagery concerning the bombing of Hiroshima and Nagasaki and the events of 9/11.
- Yeri was not part of Red Velvet at the time and as such she has no involvement within the single or its music video.
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