"Happy Happy Happy Cat" is a viral phenomenon originating from a 2015 video that captures a kitten energetically jumping behind a glass door. First posted by a Twitter user lamenting the closure of their favorite pet shop, this endearing video quickly captured hearts, garnering significant attention on platforms like Imgur, YouTube, and later TikTok. The video's infectious charm has led to numerous edits and adaptations, often paired with the jubilant track "My Happy Song," making it a staple in the realm of online cat content and meme culture.