Sorry to be getting around to this, but I want to point this out to Bryan's question.
Nippon Ichi Sofware's games ALL take place in a shared universe. although mostly contained to Post-game activities or DLC, characters from one NIS game will often show up in another. This includes ties to Hyperdimension Neptunia, The Wii's Phantom Brave, James Jones favorite Soul Nomad and the World Eaters (Speaking of deviant things on the level of bestiality, that game gets fuuuuuuuuuuuuuuuuuuuuuucked up if you play the special new game +) and Makai Wars, a game that got canceled but as an in joke the main character from this canceled game invades other games looking for work or her opportunity to finally shine in the light of day. she also has a different voice actress every time because nothing about her is ever finalized.
This element of crossing over started when Prier of La Pucelle: tactics appeared as an optional boss and recruitable character in the first Disgaea game. The ties are a little bit stronger between Disgaea games themselves, since the crossover elements tend to happen during the main game's plot like in cases of Etna showing up For Disgaea 2, Axel and Flonne being big parts of Disgaea 4, etc. That being said, I cannot think of a NIS developed Strategy/RPG that does not have SOME sort of cameo by Laharl looking to conquer other worlds or be the main character of a new game or... really, to just be a little prick to everyone.
That being said, a lot of these cameos are played for laughs, as most of the time these games tend to satirize rather than take themselves seriously. They're also kiiiinda a shared Multiverse, but Item World is essentially Multiverse hopping as it is within one game, so...