I had to laugh when I read the writeup for this song, "Medaka no Kyoudai" (The Killifish Siblings), on J-Wiki. The arranger for what would become the 3rd-ranked hit of 1983 was none other than Ryuichi Sakamoto（坂本龍一）of the Yellow Magic Orchestra. Apparently, when the song landed on The Professor's lap, he remarked "I wondered why it ever came over to me?!"
Well, I think he should take a bow for one thing. By all measures, "Medaka no Kyoudai" was a big hit in Japan. Released in December 1982, it would remain a long-running success for all of 1983, peaking at No. 3 on the Oricon weeklies before hitting the same rank for the yearly chart. It was written by Toyohisa Araki（荒木とよひさ） and composed by Takashi Miki（三木たかし）, and sung by the variety show-born aidoru trio of Warabe（わらべ）.
Warabe consisted of Tomoko Takabe（高部知子）, Atsumi Kurasawa（倉沢敦美）, and Mami Takahashi（高橋真美） who appeared on the long running TV Asahi program "Kin-chan no Doko Made Yaru no!?" （欽ちゃんのどこまでやるの?!...Kin-chan's How Far Will You Go?!） as the onscreen daughters of the host, Kinichi Hagimoto（萩本欽一）. They first appeared in 1982 when the show was given a bit of a facelift halfway through its run (1976-1986).
Cute has always been one of the tools to success in the Japanese music industry, and so it was here with "Medaka no Kyoudai", thanks to the kid-like vocals, the cute-as-all-get-out sway-happy melody and the choreography. Apparently even today, the song is being used at nursery schools all over the country. The lyrics are on the fairy tale level of things with sparrows becoming eagles and penguins, cats becoming lions and tigers, and the titular medaka (killifish) becoming carp and whales, all with the cutesy onomatopoeia. I can imagine My Little Pony and Hello Kitty coming down and sighing contentedly.