After a while the boy came into the living room where his father was talking with some friends. "Hey, Dad?" said the boy. "The bull just fucked the brown cow."
The room went silent. The father excused himself and took his son outside. "Son, you mustn't use language like that in front of company. You could say 'The bull surprised the brown cow'. Now go and watch and tell me when the bull surprises the white cow."
After a while the boy came in and said, "Hey, Dad?"
"Let me guess," said the father, "the bull surprised the white cow?"
"He sure did, Pop! He fucked the brown cow again."