The phrase comes from Brazilian reality star and bodybuilder Kleber Bambam, filmed shouting during an intense workout as he declares the monster is leaving the cage. The clip spread widely on YouTube and Brazilian social media in the mid 2010s, turning his over the top delivery into a national catchphrase. It was remixed into gym edits, football videos and everyday jokes about anyone acting wild or confident. Its mix of genuine motivation and unintentional comedy keeps it popular long after the original video.