The melody comes from Thomas the Tank Engine, the long-running British children's series about a cheerful blue steam locomotive and his friends on the Island of Sodor. The theme has been familiar to generations of viewers since the show reached television, and its bright, bouncy tune is easy to recognise even without words. Online, louder and more exaggerated edits turned that wholesome familiarity into a joke, especially for stream alerts where a donation deserves a big, silly celebration. That contrast between childhood nostalgia and sudden volume is why the clip keeps circulating in memes and streams.