Craig Robinson and his crew embark on a peace-saving mission, cruising the universe in their space shuttle, the Jupiter II. They help the peaceful Throgs in their attempts to ward off the Tyranos, a group of metallic creatures who have declared war on their planet. Jonathan Harris reprised his role as Dr. Smith. He and the Robot were the only characters from the original series to be featured in this version.
- Sherry Alberoni as Deanna Carmichael
- Michael Bell as Craig Robinson
- Jonathan Harris as Dr. Zachary Smith
- Ralph James
- Don Messick as the Robot
- Sidney Miller
- Vincent Van Patten as Lincoln Robinson