Fantasy Zone
Opa-opa, one of Sega's early mascot characters (debuting in the 1986 arcade game "Fantasy Zone"), was a frequent minor character on the show. His frequent involvement with the show led many to believe that "Fantasy Zone" was actually a spin-off series based on the character, but in reality Opa-Opa was around a year prior to the anime, and was a guest character from the start. The fact that he appears so frequently on the show is simply a testament to the character's popularity in Japan at the time.