The line comes from SpongeBob SquarePants, where the recurring background character Fred is known for yelling "My leg!" in chaotic scenes. Over time, fans clipped the shout and spread it across YouTube, TikTok, and meme edits as a quick audio cue for pain, bad luck, or slapstick disaster. Its staying power comes from how short and recognizable it is: even people who have not watched every episode often know the joke from fail videos and reaction compilations.