Dickhead is a minor character in the episode "Journey to the Center of Twayne". He is a phallusoid, a one-eyed creature with a very long neck, or head.
He "spits" on Mark Lilly when Mark and Francis Grimes go to the Dungeon in the Department of Integration to get the inmate Jerry McMillan for counseling. After spitting on Mark, Francis tells him, "No spitting, Dickhead."