A fake door, also known as a trapdoor or false door, is a special trap that resembles a real door encountered in the Luigi's Mansion series. Fake doors are designed to confuse and injure Luigi as he progresses through the games.
In Luigi's Mansion, fake doors are found in various locations on different floors of the mansion. If Luigi happens to turn the knob of a fake door, the door springs open and flattens him against the wall, causing him to lose ten HP and a few coins. There is a glitch that allows Luigi to get smashed unscathed, but only a few times before taking damage again as normal. A ghost can be heard laughing after Luigi is smashed. Sometimes, a trail of conveniently placed coins leads straight to a fake door to catch Luigi off guard.
The only way to defeat a fake door is to set it on fire; while real doors do not catch on fire, fake doors go up in flames and disappear. However, if Luigi enters two different rooms and returns to where a fake door was, it will have reappeared. During the blackout in the game, the ghosts increase the number of fake doors in the mansion.
There are several ways to tell a fake door apart from a real door. For instance, Luigi glances at fake doors as he walks by them, but he does not look at real doors. Additionally, Luigi can check his Game Boy Horror; real doors appear on the map, while fake doors do not. Luigi can also vacuum a door with the Poltergust 3000; if it rattles, it is real, and if it does not, it is a fake door. Most real doors also have doormats in front of them (an exception being the door to the Fortune-teller's Room), while fake doors do not.
Luigi's Mansion: Dark Moon
In Luigi's Mansion: Dark Moon, false doors are found within the Gloomy Manor, Haunted Towers, Treacherous Mansion, and ScareScraper. They serve the same function as they did in the first game, though Luigi now loses only five HP when hit by one (two HP in the ScareScraper) and does not lose any coins. Additionally, ghosts are no longer heard laughing after Luigi gets flattened by a false door, barring one instance in the Treacherous Mansion when a Greenie appears to laugh at him. Just like in the first game, Luigi can use his map—this time on the Dual Scream—to determine whether a door is real or not, as false doors do not show up.
Luigi's Mansion 3
Fake doors reappear in Luigi's Mansion 3, this time exclusive to the ScareScraper mode. When they trap Luigi, they do not close, forcing another player to use the Suction Shot to destroy them. They do not appear on the map, nor do they have doormats. They can be destroyed by the Suction Shot to avoid triggering them.
- Sinfield, George. Luigi's Mansion Player's Guide. Page 16. "Paper Luigi There are trapdoors all over the mansion. They are always on walls that are within full view. If you turn the knob of a trapdoor, the door will fling open and flatten you. Trapdoors don’t show on the map. If you are suspicious about a door, look at the map. If it isn’t there, it’s a trap."
- von Esmarch, Nick. Luigi's Mansion: Dark Moon PRIMA Official Game Guide. Page 28. "CAUTION The north wall contains a false door. If you interact with it, the door slams into the wall, causing a bit of damage. Use caution around any door that doesn’t appear on the Touch Screen map."