A character has aSkull for a Head. This may be because the character is a supernatural being, or due to some disfigurement that makes their headlook like a skull. Occasionally used to make a robot look menacing, with a skull instead of a head.
In all cases of this trope, therest of the body is relatively normal (i.e., not ananimated skeleton.)
See alsoDem Bones,Skeletons in the Coat Closet.