tunnel in your head

someone who never listens

"You never take my advice because you have a tunnel in your head."

croc in his pocket

a person who is stingy or cheap; usually someone who has money

"It's never Jim's turn to pay, he must have a croc in his pocket."

He only has a head to separate his ears.

a stupid person

A: "Jim got into trouble again last night."
B : "He only has a head to separate his ears."