John and Mary, both elderly residents in their 80's now live at a retirement home. The more time they spent together, the more friendly they got with each other and really began to enjoy each other's company. After about three weeks of getting to know each other, John said, "I know we are both old and can't do much sexually any more, but if I pulled out my penis, would you hold it?"
Mary didn't see anything wrong with that, so she agreed.
Every day for the next month the couple would sit outside in the park by the lake and Mary would hold John's penis. One day John didn't show up at their regular meeting place. Mary became concerned and set out to search for him.
Further down the shore Mary spotted John sitting on a bench with another woman beside him. She quickly walked up to the bench, only to find the old man's penis in the other woman's hand.
This upset her very much and she yelled at John. "We've been together for two months now. I thought we were getting along just fine. Now I find you here with this other woman. What does she have that I don't!?"
A slight smile curled on John's face as he replied, "Parkinson's."