SSB:
Ethel and Velma were both residents of a nursing home, and they both had a crush on old Floyd. But, he couldn't quite decide between the two. He would have one come to his room one night and hold his penis. Then, the next night he'd have the other old gal come and do the same thing.
Finally, he decided that Velma was his favorite, and broke it off with Ethel. "What's she got that I haven't got!" Ethel demanded to know.
"Parkinsons."