Mi-kun (ミーくん Mī-kun ): Dr. Sado's pet cat, apparently the closest he has to family. Left behind on Earth during the first season and during the 2199 series, Mi-kun is brought aboard the Yamato from the second season to Be Forever, Yamato.
- Mi-kun is based on Leiji Matsumoto's own cat Mī-kun. Mi-kun has also appeared in other Leijiverse stories such as Captain Harlock as Doctor Zero's cat.
- Mi-kun enjoys drinking sake' and Sado often shares a drink with her.
- The real Mi-kun died shortly before her debut in episode 10 was broadcast.
- Mi-kun's gender is also unclear. Although the real life Mi-kun I was female, some of Matsumoto's subsequent cats named Mi-kun were male.
- Japanese voice artist: Kōichi Yamadera (Playstation games).
- Dr. Sado's computer has a wallpaper of Mi-kun.