I've watched all episodes of this series to date, which makes me weird and/or someone with too much free time. The parent show is excellent, but this is just another mini-episode spin-off that's trying to be funny but depends heavily on you already knowing the characters. This is impossible. The original Cinderella Girls game came out in 2011 and the anime appeared in 2015. There might well be over a hundred idols in the full franchise and some of the girls here are only from the game, having had only non-speaking cameos in the anime. Even I didn't know who everyone was, although I might rewatch the parent show alongside all its silly spin-offs one day.
My favourites were Anzu (small, lazy) and Kirari (tall, cat smile). I still sort of remember quite a few others, e.g. Ranko (chuunibyou) and it is true that episodes improve if you remember the girls in question, but basically this is just lots of random teenagers being a bit silly sometimes. Season 5 is an improvement, though. Its episodes aren't unlikely to have a comedic point, instead of just filling time for a minute or two.
For what it's worth, episodes I liked in these seasons include Climax TV 45 (1980s Schwarzenegger movie parody, mostly Predator), Climax TV 51 (at the seaside, which actually made me laugh), Extra Stage 2-7, Extra Stage 15 (folk tale parody), 17 (Yukimi being a gullible airhead), 20 (Aki's idea of "sexy"), 27-28 (fishing and a doughnuts song), 33 (cooking) and 43 (Miku trying to lay down the law). The humour's gentle at best, though. I only laughed out loud once or twice. Even the better episodes are only targeting "mildly amusing". They'll occasionally bend the format with parodies, though, like the Idol Mukashi Banashi series of folk tales and the horror movie in Extra Stage 45.
The episodes aren't the important thing about this show. That would be the closing titles. There are a ridiculous number of these, each being a one-minute snippet of a real song that the girls have released, and they're often pretty cool. You can find them on YouTube. Extra Stage does a one-time-only theme song for a different solo girl every four episodes, although they've ditched the animated dancing sequences. Here's a full theme song list, from the start of Season 1, although not all episodes have a closing title song:
1. "Kira! Mankai Smile" = TV & Web eps 1-4 (my favourite, including the cute dancing)
2. "Etude wa 1kyoku dake" = TV 5-8, Web 5-9 (the song's okay, but the visuals are deliberately gloomy)
3. "Mouretsu Yonaoshi Guilty!" = TV 9 (to suit the episode, which is a Charlie's Angels parody)
4. "SUN FLOWER" = TV 10 and 12-13, Web 10-13 (bright and fun, on the beach in swimsuits and then dancing in a field of sunflowers)
5. "Kirarin Robo no Theme" = TV 11 (to suit the episode, which is a giant robot anime parody)
6. "Blooming Days" = TV & Web 14-18 (nothing wrong with this. I quite like it. They're wearing sailor suits and performing on a stage of projected flowers.)
7. "Akimeite Ding Dong Dang!" = TV 20-22, Web 19-22 (my second favourite, including the slightly sexy leg stretches)
8. "Snow Love" = TV 23-25, Web 23-26 (the song's okay. Performed in winter/Santa outfits.)
9. "Itoshisa" = TV 28-31, Web 27-29 (again, okay. I could have lived without the "chu chu chu chu" refrain.)
10. "Natsukko Ondo" = TV 32 and 34-35, Web 30-31 (I like this one quite a bit. It's in the style of a traditional Obon festival Bon dance.)
11. "Sayonara Aloha" = TV 36-38, Web 32-33 (a slower number, with sunsets)
12. "DREAMING STAR" = TV 39 (casts the girls as flower fairies. The song's fine.)
13. "Kyun Kyun Max" = TV 41-44, Web 34-36 (not one of my favourites, but it's okay. Lots of pink.)
14. "Max beat" = TV 46-48, Web 37-38 (I bet this works better as a full song than as this snippet. Nothing wrong with it, though.)
15. "TAKAMARI CLIMAXXX!!!!!" = TV 49-51, Web 39-40 (okay)
16. "Sing the Prologue" = Extra Stage 1-3, 5-7, 9-11 (it's perfectly reasonable, but I think the songs have declined a little from the early years when the parent show was still relatively recent)
17. "Haru Kokoro Frame" = Extra Stage 4 (bouncy, energetic, sung by Kamijou Haruna in front of cherry blossoms)
18. "Watashi Iro no Prelude" = Extra Stage 8 (a slower number, sung by Mizumoto Yukari in a field of flowers while holding a flute)
19. "Sekai Metsubou or KISS" = Extra Stage 12 (perfectly decent, sung by Kita Hinako)
20. "Diamond Attention" = Extra Stage 13-15, 17-19, 21-23 (the song's less interesting than the visuals, which turn the girls into katana-wielding magical warriors)
21. "Oyamatope" = Extra Stage 16 (the season's best theme song. Fun, bouncy. Sung by Munakata Atsumi.)
22. "Dangan Survivor" = Extra Stage 20 (sung by Yamato Aki, who's a macho military gun nut. This episode was funny. The song, though, is a bit unmusical, albeit also loud and energetic.)
23. "Shinobi 4.0 Ninja no susume" = Extra Stage 24 ("nin nin nin" can sod off. Sung by Hamaguchi Ayame, who's both an idol and a trainee ninja. The song has traditional twiddles, but is basically pop with lots of electric guitars.)
24. "Radio Happy" = not a theme song, but an insert song in Extra Stage 25 (seems okay, but we don't really hear it properly. Sung at karaoke by Yamashita Nanami.)
25. "Kimi no Stage Ishou, Hontou wa..." = Extra Stage 25-27, 30-31, 33, 35-36 (it's fast-paced, yet also kind of gloomy. I think it's in a minor key.)
26. "Priceless Donut Cyu" = Extra Stage 28 (another bouncy one, about doughnuts. It's quite fun. Sung by Shiina Noriko.)
27. "Omoide Janai Kyou o" = Extra Stage 32 (perfectly okay. Sung by Kitami Yuzu.)
28. "Hatsuyume wo Atana to" = Extra Stage 34 (slightly less frentic in pace than some of the others, but by no means slow. I like it. Sung by Takafuji Kako.)
29. "Life is HaRMONY" = Extra Stage 37, 39-41, 43-45, 47-48 (the last and probably the best of the non-solo Extra Stage theme songs, although not by a big margin. They even have the girls sort of performing it, although it would be generous to call what they do dancing. Pleasingly, one of them is Kirari.)
30. "Milky Mode" = Extra Stage 38 (Sung by Noguchi Yuri, who loves cows and has the biggest boobs in IDOLM@STER. I think the song's title is a reference to all those things. The song's also good fun and a lot like "Oyamotope" in its jaunty energy.)
31. "Utakata no Aeon" = Extra Stage 42 (quite good. Sung by Araki Hina, a manga-drawing otaku idol who you'll only know if you've played the games.)
32. "Manganjouju Miko no Kamidanomi!" = Extra Stage 46 (again, I quite like this one. Sung by Doumyouji Karin with lots of Shinto shrine imagery, because she's also a miko. The song is slightly traditional around the edges, but it's easy to miss.)
For what it's worth, I considered doing the same with the franchise's other theme songs. I then realised that the original IDOLM@STER had 26 different endings, one per episode, while Cinderella Girls had twelve. Plus the openings, insert songs, the 2014 movie, Puchimas and XENOGLOSSIA. (But not SideM. I didn't watch that.)
So, there you have it. A short form anime that's only occasionally worth watching, but has lots of theme songs. For what it's worth, the anime with the best theme songs are PreCure, Kodocha and Cowboy Bebop, with honourable mentions to Tenchi in Tokyo, Those Who Hunt Elves, Monthly Girls' Nozaki-kun, Zombieland Saga, Show by Rock!!, Rurouni Kenshin, Read or Die, Urusei Yatsura, Cutey Honey, Fist of the North Star, Bimbougama Ga!, Oh My Goddess and lots more.
