The Cast Show Off: A challenge of casting (and localization), as said during the Treehouse stream, was that many of the voice actors NEEDED to be this. Due to the central theme being the entertainment industry, which includes music, many of the actors involved had to be capable of singing. This likely part of the reason why the game lacks an English dub.
Fan Nickname: Variants of "Persona: Fire Emblem Edition" or "Persona Not-5" have been floating around since the trailer. Whether said nicknames are meant to be derogatory or not is dependent on the speaker.
No Dub for You: When the game was localized, it was chosen to not make a localized audio track and instead keep the Japanese audio. The team has claimed it was meant to keep up the Japanese atmosphere and setting, but, considering the steep cost of localizing music and hiring lots of voice talent, combined with the game's commercial failure in its native country, it's widely-believed that financial concerns were also a factor.
No Export for You: The "Hotsprings DLC" - which unlocked bathing suit alternate costumes for the characters - was deemed too inappropriate to localize for the NA release.
Working Title: Stainless. The original name for the entertainment agency appears to be 'Stainless Entertainment', so it is connected in some way. A few placeholder graphics also call the game Fire Emblem Tensei ~A1 version~.
The dance numbers were choreographed by professional dancers.
A lot of the original music was produced by Avex Group with professional song writers writing the lyrics.