A late-night drink

After a night on the town, a young woman brought a new friend home for a late-night drink. "You can't make any noise," she warned him. "My parents are upstairs and if they find out they'll kill us." Things started getting heated on the sofa, but after a while alcohol got the better of the man. "I have to go," he said. "Well you can't go upstairs. The bathroom is right next to my parents' bedroom," she replied. "Use the kitchen sink." So he dutifully retired to the kitchen. A few minutes later, he popped his head around the door and asked, "Do you have any toilet paper, or should I just use a paper towel?"