A five-year-old boy was sitting on a park bench with his grandpa, when two dogs began to mate nearby.
The little boy asked, "Grandpa, what are they doing?"
Grandpa, not wanting to provide 'the lecture', hesitated, then said, "The dog in the back is sick and the one in the front is helping him to the hospital."
The little boy thought for a few seconds, and the said, "That's just like people- you try to help somebody and you get fucked every time!"