No instrument invented after 1984 was allowed on this show; it was a full jazz orchestra working on the music.
Every alien shown in the series is conceptualized by a different artist, as Shin'ichirô Watanabe intended to showcase the diversity and variety of alien species in the show.
In the world of the series, everyone still listens to music on audio cassettes. Mp3s and CDs do not exist.
The closing song mentions the name "Everett". This refers to Hugh Everett III, a quantum physics expert who brought up the many worlds theory of alternate universes. In the context of the show, this points at the episodic adventures Dandy goes through.
Shin'ichirô Watanabe brought on writer Keiko Nobumoto because she had never seen Star Wars, which he felt would enable her to bring more interesting and free scripts.