Development Gag: The original Luigi's Mansion was developed with the Gamecubes stereoscopic 3D rendering ability in mind, which was ultimatively never used due the cost of the hardware needed to actually bring the effect out of a TV. Being able to have 3D effects was the reason why the sequel was developed for the 3DS rather than a home console.
Market-Based Title: The game is known as Luigi's Mansion: Dark Moon in North America and simply Luigi's Mansion 2 elsewhere.
Milestone Celebration: Part of Nintendo's Year of Luigi, the 30th anniversary of Luigi's debut in Mario Bros.. Incidentally, the inclusion of Luigi's Mansion just happened to be by chance, since it wasn't developed for the anniversary in mind. Nice coincidence, eh?