A little girl was out with her Grandmother when they came across a couple of dogs mating on the pavement.
"What are they doing, Granny?" asked the little girl.
The grandmother was embarrassed, so she said, "The dog on top has hurt his paw, and the one underneath is carrying him to the doctor."
"They're just like people, aren't they Granny?"
"How do you mean?" asked the Grandmother.
"Offer someone a helping hand," said the little girl, "...and they screw you every time!"