Another one starts the same way...
A husband is in bed next to his wife in the dark and starts running his hands over her body. Knowing what he wanted, she rolls over and says, "I'm sorry.. we can't tonight as I have a gynecologist appointment tomorrow and I want to stay fresh for it." The husband frustratedly rolls over and closes his eyes.
A few minutes later he opens his eyes, rolls back over toward his wife and asks, "Well, you don't have a dentist appointment tomorrow, do you?"