BirthDayParty is a feature in THE IDOLM@STER MILLION LIVE!: Theater Days to put more emphasis on character birthdays, with a celebration with other idols and the Producer.

Previously, an idol's birthday celebration would only include a special line for the hallway opening scene and a custom whiteboard design.

Date Idol Whiteboard Entrance Line BirthDayParty Line Happy Birthday Line
July 4 Hinata Kinoshita Hinata Kinoshita BirthDayParty 2018 Whiteboard あのね、〇〇P。

今日誕生日なんだけども…あたし、 ちょっとは大人になったんかなぁ?

みんな、ありがとねえ。うれしくって泣きそうだべさ。 これ、帽子かい? りんごのブローチがついてる……。