- Actor Allusion: The four ribbons that Natsumi finds for them to wear at the singing competition has the same colors as their respective voice actress uses in Sphere and for their solo concerts: Purple for Natsumi/Minako, pink for Saki/Ayahi, orange for Yuka/Haruka and green for Rinko/Aki.
- Anime First: Not quite (the manga began in January), but it's fairly obvious that it was originally designed as an anime since it's a vehicle for idol group Sphere.
- Fan Nickname: Since the show started airing, a large number of viewers refer to the main girls by their hair color:
- Natsumi is Orange.
- Saki is Yellow.
- Yuka is Green.
- A more specific nickname for her is Green Saten, due to the similarities to Ruiko Saten.
- Rinko is Pink.
Trivia / Natsuiro Kiseki