The Buff Baby song comes from Cartoon Network's Adventure Time, where a flashback shows Finn as a baby singing and dancing for Jake's family. The short scene was clipped and shared for years as a reaction and remix, then found new life on TikTok and YouTube edits where users imitate the dance or paste it over other characters. Its simple, repeatable hook and Finn's unmistakable voice made it easy to recognise, which is why the baby flex joke still circulates long after the show ended.