CAUTION: This one is sort of mean spirited, but still funny.

Guy takes his wife to the Doctor...

The Doc says, "Well, it's either Alzheimers disease or AIDS."

"What do you mean?" the guy says, "You can't tell the difference?"

"Yeah, the two look a lot alike in the early stages... Tell you what... Drive her way out into the country, kick her out of the car, and if she finds her way back, don't fuck her."