To ask for something enormous or unreasonable - maybe impossible to obtain. The woman is asking for the moon. She will never get what she wants.
Very tough, not easily moved by feelings such as pity. The old lady is as tough as an old boot and never shoes her feelings at all.
Very sick. My friend was as sick as a dog when he left the restaurant last night.
Dishonest. The politician is as crooked as a dog's hind leg and nobody trusts him.
Very comfortable, very familiar. I felt as comfortable as an old shoe when I entered my aunt's house.
To argue only to be different. My brother always argues for the sake of arguing.
Someone or something that is very precious or important to you. The man's youngest daughter is the apple of his eye.