Luigi's Mansion: Dark Moon is called Luigi's Mansion 2 in the Japanese and European releases. It was also refered to as this in the first prerelease materials, as well as with the Nintendo Switch version.

The first letters from the names of the five playable mansions spell out the word GHOST.

Gloomy Manor
Haunted Towers
Old Clockworks
Secret Mine
Treacherous Mansion

The first letter of each of the five possessor's (boss ghosts) names spell out the word GHOST.

Grouchy Possessor
Harsh Possessor
Overset Possessor
Shrewd Possessor
Tough Possessor

The binary code message the ComBooter says to you actually translates to 'BOO'.

At the beginning of the game, if you look beyond Luigi, you can find the map from the beginning of the first game.

The house Luigi lives in is actually the Rank D house built for him at the end of the first game.

The opening scene in which Luigi is sleeping in front of a TV which suddenly displays static, awakening him and causing him to reach out towards it, is a reference to the 1982 film "Poltergeist".

When you first get a video call from E.Gadd on the first mission he says the he was worried that the battery life on the Duel Scream might die so he turned down the brightness so it would be good for awhile. This is actually a joke about the original DS' short battery life since the Duel Scream is in fact a modified DS.

The music which is played in the elevator is the same tune which is heard at the pause screen in Mario Strikers Charged, a previous Mario game which was also developed by Next Level Games.

In the Treacherous Mansion, the spears which the Greenies use have Kalimba Tiki mask on them from "Donkey Kong Country Returns".

The scene in the Hollow Tree level, in which Luigi looks down the staircase, is a reference to a movie called "Vertigo" and the camera effect named after it.

There is a cutscene in Treacherous Mansions in which two Strong Greenies bring a suit of armor to life. This is a reference to the film "Frankenstein".

The First edition of Luigi's Mansion 2 released in Europe received glow in the dark covers.

In the French translation, the first letter of each bonus mission in order reads "Luigi".

While Luigi normally calls out "Hello" or "Yoohoo" when the + Control Pad is used, in the later missions in the Treacherous Mansion, and after finishing the game, he will instead call out "Mario" as a reference to the original Luigi's Mansion.

According to a Swapnote Message sent by the Game's Producer, Shigeru Miyamoto, the Polterpup is his favourite Ghost in the game.

In the Scarescraper, one of the bosses is called Fright Knight, his description reads;

"Rumor has it that this Greenie comes from the middle ages, where he was a knight searching for the kidnapped princess. Sadly, wherever he went, she always seemed to be in another castle"

The last bit is obviously a nod to Super Mario Bros. on the NES, where Princess Peach was always in another castle.

During an interview the game producers said that the mission where the player leads Toad out of the Mansion was inspired by leading Zelda out of the Castle in The Legend of Zelda: A Link to the Past.

When starting a mission in Gloomy Manor, there is a chance that Luigi will be teleported into the mansion landing on the Poltergust rather than on his rear.

In a 2013 interview with Polygon, director Bryce Holliday revealed that Luigi's portrayal in the game was influenced by the 1990 British comedy series Mr. Bean. The show served as reference material for Luigi's animations and characterization, with Holliday noting parallels between Luigi and the show's title character as a "hapless fool and reluctant hero." Holliday also felt that these similarities would help audiences sympathize with Luigi, which in turn would supplement the comic relief that his reactions and mishaps provide.