Possible Clues:

• Head copper guarding princess's millions
• A nut-case?
• Brainpan
• The skull, major head bone
• Board game with the categories "Data Head" and "Word Worm"
• Skull with key element lacking on top
• Board game with the categories 'Data Head' and 'Word Worm'
• Skull, bones enclosing brain
• Mental case
• The skull, bone enclosing brain