Patrick's alter ego in "Survival of the Idiots"; he argues he is in fact Dirty Dan. He is not; SpongeBob is. Also he makes the awesomest face when he asks "Who you callin' Pinhead?"
One who lacks the intelligence of the "normal" sector of the human population; even so cannot handle the most mundane of tasks due to the lack of common sense and intelligence.
Some one who has a small head for their body size. Also can be characterised by a small jaw and/or large ears. Obviously, some one with a small head, receeding jaw and large ears can be described as "piphead extremis".
While watching the TV we noticed that the presenter was a Piphead. The more we looked the more obvious it became.