Basically I use this to explain the animal like behavior in ghosts in horror movies/games
Ghosts are humans/creatures that are just sort of in a state of nonexistence. Just hanging out in heaven, hell, or just hanging out in the living world.
But Human Ghosts have this thing where sometimes (Maybe in a stressful situation) their mind goes into "Creature mode" where they'll lose their consciousness, but will still be awake, and their mind is now just acting on instinct. Their body will change to have more "animal" like features (mostly just raptor looking legs, animal teeth, but their mouth, and eyes will become larger. The mouth will commonly look like a large smile almost spreading to the back of their head. Their eyes will droop. Their pupils/irises will dilate. Their nose will maybe disappear leaving a skull like nose hole in it's place. They'll grow taller (Depending on their age, and height.), They'll become skinny to the point where you can see their ribs because the skin/flesh stretched. Their arms, and legs will have this pitch black scaly skin (kind of like lizard skin) that covers half of the arms/thighs, but will cover the whole wrists/hands/knees, and their toes/fingers will become claws. If they have good memories of a person they'll not attack that person, though if they have bad memories of a person (Example: The person treated them badly, or has hurt them physically/mentally) then they'll attack, and hunt that person, and eat their dead corpse. They'll act like how an animal acts (Like picking up people they like by the "scruff" (aka loose clothing that is far enough from the skin), Making animal noises (Like bird, dog, cat, lizard, or any animal noises, and acting like u'know- animals?-), and They'll have movements similar to animals (like dogs tilting their hands, walking on all fours (sometimes-), or playing like a cat/dog.)