A husband went to buy a birthday gift for his wife. Some friends had been invited over that night to celebrate her fortieth, and he wanted to get something special. At the store he spotted some cute little music boxes. One blue one was playing "Happy Birthday." Thinking they were all the same, he chose a red one and had it gift-wrapped.
Later, at dinner, he gave it to his wife and asked her to open it.
When she lifted the lid, out came the tune to "The Old Gray Mare, She Ain't What She Used to Be!"