An abnormally large head with the focus of the mass in the uppermost regions.
Note: When people with watopolis heads are toddlers, the direction of their movement is largely dictated by the gravitational forces applied to the head, since it contains the majority of the mass of the body. It often attempts rebellion and moves independently of the thoughts and requests of the body, much to the toddlers dismay.
The Brain from Pinky and the Brain..
That guy that comes into the movies/play/any staged performance late and sits directly in front of you...
"Did you see Sarah and Jack's baby? He was cute but he had a watopolis head!"
"Shut the hell up! With that big ass watapolis head!"