Crackers

A Corkman once visited his psychiatrist and told him that he thought he was turning into a packet of biscuits.
"What sort of biscuits?' asked the psychiatrist.
'Square ones', said the Corkman.
'With little holes in them?' asked the psychiatrist.
'Yes doc', said the Corkman with relief, 'That's it exactly'.
'You're crackers', said the psychiatrist.