ERROR Night (previously known as Night #) is the hardest fan-made night in Abandoned: Discovery Island. Only ERROR Mouse becomes active.
In order to access this night, the player must type "ERROR" on Title Screen, which makes him appear instead of PNM, and then click on his nose. This will grant access to this night.
The player must keep an eye on cameras at any time to know where ERROR Mouse is. If it entered the office, the player must shut off the camera, but not all of them. Also the player needs to use less power, so it will never run out. If it ran out, the player cannot do anything, as soon as it jumpscares the player, eventually ending the run. Hiding will also work against him, but it can be used only five times.
If the player survives this night, he will "jumpscare" the player and will restart the game. After that, his content on Extras Menu and Custom Night will be unlocked.
- This night is based of the Secret Night from Five Nights at Candy's: Remastered.
- It's the only night where the player can't shut off the power.
- The cutscenes were planned, but they got scrapped.