Crawler zombies are skinny zombies who run around on all four limbs. Based on their appearance, Crawler zombies seem to be mutated much more than regular zombies. Richtofen gives an explanation that they were a failed experiment of some sort. They have a slimy, greenish gray shade of skin and appear to be wearing only torn brown jeans or jean shorts. They emit a very distinct trail of green gas that makes them quite noticeable among the horde. Furthermore, they have not retained their human facial features, and instead an over-sized angler fish-like mouth is the only prominent feature on the face.