Mr. Smith telephoned the doctor in the middle of the night.
"Come quickly, Doctor! You know my wife sleeps with her mouth open. Well, a mouse has run inside her!"
"I will be with you in about ten minutes," replied the doctor. "Until I arrive, try holding a piece of cheese in front of her mouth. This may bring the mouse out."
When the doctor arrived, Mr. Smith was not holding a piece of cheese. He was holding a fish in front of his wife's mouth.
"What are you doing?" asked the doctor. "A mouse doesn't like fish."
"I know," said Mr. Smith, "but we have to get the cat out first."