Casey Jr is the small circus train that carries Dumbo and the other performers in Disney's 1941 animated film Dumbo, and its distinctive whistle became part of the character's cheerful personality on screen. The train later appeared in Disney parks and other animated appearances, keeping the sound familiar to generations who grew up with the film. Online, creators reuse the whistle as a shorthand for trains, circuses and old-fashioned cartoon charm, because listeners recognise it instantly even without seeing the train itself.