In episode 2, the producer has a list of idols/groups scheduled for events, and pens the Hacka Dolls into one of the slots to fill space.
I suspect that all of these are references to other idols or idol-like entities. Going down the list:
- まつだひじりこ "Matsuda Hijiriko" → Matsuda Seiko (kanji pun on 聖)
- "u's" → μ's
- "Sit Down Girls!" → Wake Up, Girls!
- 美少女ハリウッド "Bishoujo Hollywood" → Shounen Hollywood
- でんじは組,etc "Denji wa Kumi, etc" → ???
- ミス・カラフール "Miss Colorful" → Miss Monochrome
- スーパーソニ男 "Super Soni-o" → Super Sonico
- (Hacka Doll)
- 珂那ちゃん "Kana-chan" → the fleet's idol, Naka-chan
- ワン子クラブ "Wanko Club" → ???
- 長森明菜 "Nagamori Akina" → ???
- ゆりかおる "YuriKaoru" → YuiKaori
- Square → ???
I haven't managed to figure out the referents of the four ones I've bolded above. Who all are being referred to here?