The Anteroom is a location in Luigi's Mansion and its Nintendo 3DS version.
Description[]
The Anteroom is a short hallway with only three cabinets, each with a blue vase on top, and two chandeliers hanging from the ceiling. It is accessed from the door on the northern wall of the Parlor, and the Anteroom's left wall has a door leading into the Wardrobe Room.
In Luigi's Mansion[]

Luigi traveling through the Anteroom, which has its lights turned on
The Anteroom is accessed in Area One, and is the third overall room visted by Luigi. Luigi can access the Anteroom from a door on the northern wall of the Parlor. The first time Luigi enters the Anteroom, the doors are blocked by spiky barriers, and Luigi has to vacuum up four Gold Ghosts and two Purple Punchers, which first appear in the Anteroom. After Luigi captures every Ghost into his Poltergust 3000, the lights turn on and the spiky barriers vanish, enabling Luigi to either exit back into the Parlor or continue on to the Wardrobe Room.
After the Boos are freed from the Storage Room, Luigi can find a Boo named Bootha in the Anteroom, hiding in one of the three cabinets.
During the blackout, Luigi is required make his way through the Anteroom, after the Parlor, to continue into the Wardrobe Room, where Uncle Grimmly is fought. Only one Purple Puncher and four Gold Ghosts appear in the Anteroom during the blackout, and Luigi is not required to vacuum them up.
In European and Australian versions of the original Nintendo GameCube version, the Hidden Mansion has three Purple Punchers, one Blue Twirler, and several Blue Mice. A Speedy Spirit can also be found in the northwest cabinet.