One would think that a multibillion dollar global corporation like Namco Bandai, wouldn't have Gratuitous English and "Blind Idiot" Translation, as seen in song titles or advertising posters. Corporate interviews have proven they have professional English translators on staff, and the company has localization offices in the USA and UK. A quick email or phone call gets access to these resources with minimal cost and a one day turn around. Then again, maybe they just don't care about it...
The most likely answer is that they deliberately do so, just to spice them up. Remember the fact that none of the idols (save for the foreign-born ones) are known to be fluent and perfect English
In the last episode of the anime, Ritsuko go on stage with the girls to sing the song "Itsumade mo,Dokomade mo", wich is nice and all, but it doesn't explain why was she wearing a stage outfit identical to the one of the girls are wearing in that moment? Early in the episode, she's clearly wearing her suit. One could say that she wore when she was proofing it, but she wouldn't be wearing it after the girls were already on stage. Of course, the Producer or the President, or even Kotori could have delayed her or something, but since nothing is shown onscreen, or even implied, it just comes as a little too convenient to not break the Suspension of Disbelief.
Maybe because it was a last-minute decision.
This was one of the Mythology Gags from Idolmaster 2 (a similar event occurred at the end of Ritsuko's route in the Playstation 3 version's Extra Episode, but in the anime this event was hinted at earlier in the episode when Ritsuko asks Ami what's in her bag. Note how the twins replied - it's the stage outfit in question.
In iM@S 2, Yayoi always has her arms raised up to her chest as if about to cheer. ALWAYS. She stands like that, she walks like that... Is that even healthy?
At least for me I've never heard it was unhealthy.
How come four of the Cinderella girls get Figma figures before any of the main girls?
Cinderella Girls has a larger player population than the main iM@S titles, most likely because it's a mobile phone game and there's at least one idol a person will like.
In episode 7, what was Yayoi doing in the kitchen all the afternoon when bean sprouts were raw to be cooked in the table and the melon soup don't take that much to prepare? She's even seen cutting butter but apparently none of the recipes she made contain it.
Azusa's entire motivation for becoming an idol is to find a potential husband. Does she not realize that having a boyfriend when you're an idol is a very, very bad idea? If she successfully found her special someone, her fans would abandon her. If her career ever took off, she would have to pretty much abandon her dream of getting married until it's too late.
There's actually a bit of Fridge Brilliance behind this. In the first console iM@S, when Azusa first meets the Producer, she immediately wonders aloud if he's the Destined One. From that moment on she sticks by the Producer for her idol career. Yet while being under his care, she's rather flirtatious, schemes up situations where he's posing as her fiancé (or subtlety dating), and gets REALLY angry at people who insult him. She never minds if he's a bit perverted and quickly accepts he stole her Sacred First Kiss. In short, Azusa had Love at First Sight for the Producer: becoming an idol was only a pretext for being with him on a constant basis. Even putting that aside, in the other renditions of iM@S, Azusa has indicated she might quit being an idol upon finding her Destined One. The career is a means to an end, rather than the actual end itself. Given that by canon the Producer is her Destined One, the game simply handles the situation by having their relationship being a secret.
While this could've just been a case of her in-universe fans disregarding the Contractual Purity or her massive fame overriding it, Mai Hidaka had left the idol business when pregnant with her daughter Ai (she'd have to have had sex at some point during her career), and was still capable to make a comeback much later on (and much older than Azusa currently is now) after her daughter debuted as an idol herself. It's entirely possible that breaking Contractual Purity simply doesn't mean as much in this universe as it does in Real Life.
Regarding Side M.... Why the hell would some of these men with very high paying, important, respectable jobs quit their current job and become idols? For instance, Kaoru Sakuraba is a former surgeon. He went through medical school, likely saved countless lives... And decided to leave that in favor of becoming an idol?
For Kaoru specifically, given his backstory regarding his Cool Big Sis the reason he left being a surgeon could have been to do with her - just as becoming a surgeon was to do with her. But just because you may have a high-paying, important, respectable job, does not necessarily mean you're happy with it or with life.
In the Nemuri Hime trailer in the movie: How could Iori do all those stunts during the fight with Yayoi? I mean, she isn't even very athletic and according to trick-turorial pages those are in advanced level and it takes you a lot to learn basic stunts, in fact what she did is what only a professional gymnastic does, not even Makoto can do a fight scene like that.
In the post-trailer commentary, Miki stated that the movie is CG-heavy. Through that statement, it may be taken for granted that Iori's movement is computer-generated using professional gymnastic athlete in her place (which happens, mostly, to have approximately same size as Iori).
Akizuki Ryo. Why does no one from his school, friends, family, or anyone else even suspect that the nation-wide famous idol and the boy with the same face and name might be related? And how is he treated at home/school now that he has outed himself as a (former) crossdresser? Granted, I only read the manga, but is this aspect explored in the game?
Why is Ryo's actual gender a secret while Saki from Side M is openly a crossdesser?
315 Pro is explicitly a male idol agency, and the opposite is probably true for 876. Even if 876 did have male idols, Ryo was introduced as a female idol to replace a no-show; they probably had no choice there but to keep up the charade.
Why do female-focused agencies like 765 or 346 have idols who are no older than 25-27 while 315 which is male-focused even has +30 idols?