Yukino Yayoi is seen to have a tiger-striped cat in the series. This cat is a trademark of creator Leiji Matsumoto, and is affectionately known as "Leiji," after his creator.
In creating the "Queen Millennia" manga, Leiji Matsumoto was inspired by the Japanese folktale "Taketori Monogotari," or "The Tale of the Bamboo-Cutter": a princess from a magical kingdom in the moon is adopted by a bamboo-cutter and lives amongst humans for a time. Another title for this series is "Shin Taketori Monogatari," or "The New Tale of the Bamboo-Cutter."
In the series, Hajime attempts to reach a compromise between the peoples of LaMetal and Earth, and at the end he tries to help people escape from La-Metal by using a helicopter. However, in Reine Des Millénaires (1982) he is a student of Yayoi and flies an A6M Zero fighter plane into battle with LaMetal's troops. Another difference is in the "Queen Millennia" manga, where he receives a cybernetic implant which increases his intelligence and enables him to fly space ships.
The series was originally scheduled to have 52 episodes, but due to having lower ratings than its predecessor Ginga Tetsudo 999 (1978), the series was completed with only 42 episodes.
While Yukino Yayoi is canonically Professor Amamori's private secretary, in the series and "Queen Millennia" manga she lives on the second floor of a ramen shop, run by the couple who have adopted her. In Reine Des Millénaires (1982) she serves as a teacher at Hajime's school, and lives in a high-class apartment.