The sound comes from Charlie the Unicorn, the flash-animated comedy series by FilmCow that became one of the first major viral cartoons on YouTube in the mid-2000s. In the sketches, the grumpy unicorn Charlie is constantly led into surreal misadventures by two cheerful unicorns, and his exasperated reactions became quoted endlessly online. This banana line is one of his most repeated complaints, and like other Charlie the Unicorn clips it survives as a reaction sound for absurd or annoying moments rather than fading with the series.