An old man and an old woman, who lived near each other in a large apartment complex, soon became friends after each one lost their spouse. Every Saturday evening at 6:00 pm sharp, the man would visit the woman's apartment, bringing a rented video. Then she would serve him some wine, cook him dinner, and they would sit on the sofa and watch the movie together. During the movie, she would unzip the man's pants and place her hand on his penis. This same sequence of events would occur each and every Saturday evening. Then one evening the old man didn't show up. The old woman decided to do a little investigating. She watched him leave his apartment and head to the apartment of Mrs. Renfrow, another widow down the hallway.
Then she decided to confront him about the other woman. She told him, "You know when you didn't show up last Saturday, I got suspicious and watched you leave your apartment and saw you enter the apartment of Mrs. Renfrow down the hall. What gives? What does Mrs. Renfrow have that I don't have?"
The man replied, "Parkinson's."