In a mental institution, a nurse walks into a room and sees a patient pretending he's driving a car, with his hands at 10 and 2. The nurse asks him, "Charlie! What are you doing?"
Charlie replied, "Can't talk right now.... I'm driving to Chicago!"
The nurse wishes him a good trip and leaves the room. The next day the nurse enters Charlie's room just as he suddenly stops driving his imaginary car and she asks, "Well Charlie, how you doing?"
Charlie says, "I'm exhausted, I just got into Chicago and I need some rest."
"That's great," replied the nurse, "I'm glad you had a safe trip." The nurse leaves Charlie's room, and then goes across the hall into another patients' room, and finds Ed sitting on his bed masturbating vigorously. Very surprised she shouts, "Ed what are you doing?"
To which Ed replies, "Shhh, I'm screwing Charlie's wife, while he's in Chicago."