"Once Upon a Planet" is the ninth episode of the first season of the American animated science fiction television series Star Trek. It first aired in the NBC Saturday morning lineup on November 3, 1973, and was written by American television writers Chuck Menville and Len Janson. Set in the 23rd century, the series followed the further adventures of the crew of the Federation starship Enterprise, continuing on from the original Star Trek series. In this episode, the crew of the Enterprise re-visit a "shore leave" planet for R&R but quickly find themselves under attack. Source: Wikipedia (en)