Mirror

A Mirror is a reflective surface that displays the reverse image of what is in front of it. As such, mirrors are typically used for personal grooming. However, the mirrors in Luigi's Mansion serve another purpose. If Luigi examines a mirror with his Game Boy Horror, the green-clad plumber will be instantly warped to the Foyer, the main entrance of Luigi's Mansion. Every mirror in the mansion (except the room-length mirror in the Mirror Room) is magically connected to the mirror in the Foyer. Additionally, if Luigi examines the Foyer mirror, he will simply warp to the Foyer (i.e. he will remain in the same place).

These magical mirrors can be used to create short-cuts when necessary (instead of walking through the entire mansion), return to the main entrance if lost in the mansion, or even (if needed) escape powerful enemies (if Luigi can examine the mirror fast enough before being attacked). Interestingly, the only way to exit the Sealed Room is to use the mirror located in the room (as the door is sealed up and Luigi cannot climb up the chimney, the entrance to the room). Some mirrors are covered with a piece of cloth, meaning Luigi has to remove the cloth with the Poltergust 3000 before he can use the mirror.

Finally, one mirror in the mansion serves its regular purpose by showing the reflection of a wall switch Luigi needs to activate in the Storage Room.

Trivia

 * Unlike other games, where hints about certain features will be provided by characters or signs, the player is never informed that the mirrors can be used to warp to the Foyer. The only way for a player to figure this out is to have Luigi experiment with the Game Boy Horror and accidentally examine a mirror.
 * Originally, a line of coins led to the wall switch in the Storage Room. Later in the games development, programmers decided to remove the trail of coins in favor of the reflective mirror.