The squeak comes from the small air valve inside squeeze toys, which forces air through a reed when the rubber body is pressed and released. Rubber ducks became a familiar bath toy during the twentieth century and their noise soon stood in for anything small and harmless in cartoons and comedy sketches. Online, the isolated clip spread through soundboards and short video edits, where creators reuse it as a clean, copyright free style punctuation sound that needs no context and reads instantly even on mute captions.