Does "Moe Moe Kyun" mean anything?
While of course the word "moe" is Japanese slang with a particular meaning that doesn't really translate to English, it's for a very specific type of cute, and the entire phrase is supposed to sound sort of like cutesy nonsense (which as far as I know, not really grammatical at least according to Japanese textbook).  However, Moe moe kyun has also become somewhat of a meme - a sound to indicate something is sooooo cute. Sort of like baby talk I guess. According to Urban Dictionary, Moe moe kyun was used in the anime K-On!

I don't recall whether Moe Moe Kyun was literally used in the Japanese dialog for Disgaea 3 or not, but I do know that in general, the translators for the Disgaea series have been known to insert direct anime and video game references even when they weren't there in the original Japanese script. For example, in Disgaea 4, Fuuka yells "Objection!" in the English translation (reference to Phoenix Wright), but I'm pretty sure she did not say the equivalent in Japanese (「異議あり」　"Igiari!").  But, anyways, I would not be surprised if it were inserted in the English as an actual reference to K-On!, or perhaps it was even there in the Japanese as a K-On! reference.