Fake door

Trapdoors (also known as Fake Doors) are special traps designed to resemble real doors. They were placed throughout Luigi's Mansion to confuse and injure Luigi during his quest to rescue his brother Mario. If the green-clad plumber happened to turn the knob of a Trapdoor, the door would spring open and flatten Luigi against the wall, causing Luigi to lose 10 HP. Interestingly, a ghost could be heard giggling after Luigi was smashed. Sometimes, a trail of conveniently placed Gold Coins would lead straight to a Fake Door to catch Luigi off-guard.

To determine if a door was real or fake, Luigi could check his Game Boy Horror. Real doors appeared on the map, while trapdoors didn’t. Additionally, Luigi could vacuum a door with his Poltergust 3000. If the door rattled, it was real; if the door did not shake, it was a trap. Interestingly, Trapdoors would only lead north (if they could actually be entered). Any door that led south, east, or west was always real.

The only way to defeat a Trapdoor was to set it on fire. The door will go up in flames and disappear. Real doors would not catch on fire.