“Cowabunga” is a long-running American pop culture catchphrase that became especially associated with the Teenage Mutant Ninja Turtles, who used it as an energetic exclamation. Online, the clip spread as a quick reaction sound for moments that feel bold, reckless or absurdly confident. Its staying power comes from how short and recognizable it is: viewers immediately understand the mood, whether the edit is celebrating a huge move or setting up a crash, wipeout or joke reversal.