This sound comes from the viral Lego City commercial quote that begins with "A man has fallen into the river in Lego City" and opens with a quick "Hey!" The ad circulated for years online, then became a widely reused meme format in short edits, remixes, and parody voiceovers. Even on its own, the opening shout stayed popular because it is instantly recognizable to people who know the meme and because it works as a clean, simple attention-grabber in comedic timing.