The shout comes from SpongeBob SquarePants, the long-running Nickelodeon animated series, where a recurring background fish, Fred, yells My Leg whenever he is injured in a scene. The line became a running gag across many episodes, and fans later clipped it into compilations and reaction edits. As short-form video grew, the four-second cry spread as a ready-made punchline for fails and accidents, because listeners recognise the reference instantly. Its simplicity and exaggerated delivery have kept it in regular use long after its first appearances.