In the hallways, a mystery door will appear. The door will connect to a mystery room which is completely pitch-black with various multicolored question marks floating around the room. It contains a random item that is considered rarer than normal, such as a Dangerous Teleporter, An Apple for Baldi, or a Grappling Hook.
While in the mystery room, most NPCs cannot enter the room on their own, with The Test being the only exception, though the player can use items such as a BSODA to push an NPC inside. While the player is in the mystery room, NPCs will stop moving if they try to chase after them. However, Baldi and an angry Dr. Reflex may hear the sound from the mystery room door and will try to open it.
The door will disappear when 90 to 120 seconds pass. The player can remain inside of the room as long as they like after the door disappears but will not be able to re-enter it once they leave.
An Apple for Baldi in the mystery room in Endless Mode - Medium.
The mystery room always contains An Apple for Baldi. Unlike in randomly generated levels, there are two lamps attached to the ceiling and there are no question marks, both being the result of the outdated level generator that was used to generate this.
Map color of the mystery room in Endless Mode - Medium.
Unlike in randomly generated levels, there is a color for this location in the map, white.
Other appearances[]
A mystery room door in one of the promotion screens.
Since V0.3.8, after the end of the event, the sound of locking the door is played to signify the door to the mystery room disappearing.
Prior to V0.1.3, the event would instead last from 45 to 60 seconds.
From V0.3.5 to V0.3.8, characters could be teleported to the mystery room via whirlpools during the flood event. However, this still happens in pre-made levels.
The flood in the mystery room viewed from the Principal's office.
The mystery room could be seen through the windows in the Principal's office or faculty room, even if the event is not active. Since this version, windows cannot be generated to a mystery room.
The mystery room did not have multicolored question marks. However, this still applies to pre-made levels.
Arts and Crafters could teleport the player to the mystery room without the mystery room event starting.
A mystery room with two doors could spawn.
The room color was white in the quick/advanced map.
From V0.4 to V0.5, the color was green in the quick/advanced map.
Prior to V0.5.1, if the player bought the map fill favor from Johnny's Store and the floor had a possibility of spawning a mystery room, the location of the mystery room would still appear on the map even if the door to the room had not appeared yet. This could be exploited to always know where the mystery room was, without needing to find it.
Since this version, even if the player enters a mystery room, it will not feature on the map. This does not apply to pre-made levels.
Prior to V0.6, the announcement of the event read "A mystery room has appeared! Find it before it disappears!"
Glitches[]
Baldi's Basics Plus[]
Rarely, the player can see the black texture when starting a level.
If the player moves the camera, the black texture will disappear.
A mystery room with tiny holes below the door.
Sometimes, there can be tiny holes below the wall.
A darkened item in a mystery room.
Rarely, an item that's inside of a mystery room can be darker than usual.
Baldi's Basics Kickstarter Exclusive Demo[]
In V1.0, the characters would get locked inside the mystery room when entering. It could be used to trap Baldi inside, allowing the player to freely complete the level.
