Nightmare Mangle is a non canon Nightmare Animatronic. It appears in the Five Nights at Freddy's 4 Haloween DLC. Nightmare Mangle replaces Nightmare Foxy in the Halloween Edition, and thus almost shares the same behavior.
Nightmare Mangle behaves almost exactly like its counterpart, Nightmare Foxy. It is first introduced on Night 2. It will try to enter the Bedroom from either hall, despite it not appearing within the hall. If it succeeds in doing so, it will then enter the Closet. Like Nightmare Foxy, at this point, if the player fails to check the Closet frequently enough, then Nightmare Mangle will come out and attack the player. While Nightmare Mangle is in the closet, static noise will play, making surviving far more difficult, because it drowns out most audio cues.