This creature appears to have a thin pale layer of skin making it look boney, it has an almost human anatomy other than it's gaping mouth which makes it look as if it's laughing. It has no eyes or nose leaving indents where we assume they would be, indicating it probably once had a nose and eyes. It's mouth has no oral cavity(teeth, tongue...etc.). It has long slim arms, the photo is blurry making it hard to see whether it has fingers or even hands at all. We can't see the rest of the body due to the darkness.
In his CuriousCat profile, he says that it is harmless, and that it is something that happens sometimes, and you just have to wait it out.