Underground Ernie was a British computer animated children's television series produced by Joella Productions in the United Kingdom on the BBC on both CBeebies and BBC Two, and sold around the world by BBC Worldwide. It is set in International Underground, a fictional worldwide underground railway network, based on the London Underground, and focuses on the everyday adventures of Ernie, a friendly underground supervisor, Millie, his multilingual colleague, and Mr. Rails, the lovable maintenance man.