*Monster Rat (Formerly known as "Nightmare Rat") is a monstrous manifestation of the original Rat that appeared in Five Nights at Candy's 3 as one of two main antagonists alongside Monster Cat. Monster Rat's appearance closely resembles that of a human with both fixed ears, pointy fingernails, stitched parts, and surprisingly, sporting a long, rat tail filled with metal pieces. His face seems to sport fangs, glowing red eyes, and a big nightmarish smile.

Unlike his other counterparts, Monster Rat is a living creature. Monster Rat starts outside the Bedroom. If the player hears thumping and sometimes knocking, it means he is either hiding at the door, in the wardrobe, or in the closet. The player must shine their flashlight at these locations to force him back.

If the player does not force him back in time, he will enter the room. He will stand in one of 3 locations in the room, and a purple-blood like an effect will appear around the player's view. The player must shine their flashlight at his eyes. This is easier said than done, as Monster Rat will try to dodge his head around to avoid the flashlight beam. After about 10 seconds of this, the flashlight will flicker, and Monster Rat will go underneath the bed.*