On the planet New Aries, Jim Marlowe (Benny Grant) befriends a small alien that he names Willis (Pat Fraley). While attending a boarding school, Willis helps Jim discover that the school's headmaster Marcus Howe (Roddy McDowall) is scheming with General Beecher (Nick Tate) to re-open the mines after Jim's mother ordered them shut down.
- Adaptation Species Change: Owing to the miniseries taking place on the fictional New Aries rather than Mars, Willis and the planet's inhabitants are not Martians in this version.
- Adapted Out: The miniseries omits Frank Sutton, with Jim's sister Phyllis "PJ" Marlowe fulfilling the same role Frank played in the original book.
- Animated Adaptation: An animated miniseries based on a book.
- Bald of Evil: General Beecher is the main villain of the miniseries and is depicted as bald.
- Composite Character: Jim's sister PJ replaces Frank Sutton's role as Jim's human companion and roommate at the boarding school, when in the original book she stayed home and had minimal involvement in the story.
- Distant Finale: The miniseries ends 70 years later, where the environment of New Aries has been restored to its non-polluted state and a fully metamorphosized Willis has befriended Jim Marlowe's granddaughter Jamie.
- Mini Series: The series consists entirely of a three-part story.
- Never Say "Die": Played straight when Willis explains to Jim that he won't live to see him again when his hibernation is finished. Jim only asks if he won't be alive.
- Robotic Reveal: Jim, PJ and Willis are at one point captured by three men who turn out to be robots when their masks are removed.