Guy: Doctor, my girlfriend is pregnant but we always use protection and the rubber never broke. How is this possible?
Doctor: Let me tell you a story: There once was a hunter who always carried a gun wherever he goes. One day he took his umbrella instead of his gun and went out. A Lion suddenly jumped out in front of him.
In order to scare the Lion, the hunter used his umbrella like a gun and shot the Lion and it died!
Guy: Nonsense!! Someone else shot the Lion...
Doctor: Good! You understand the story.
Next Patent Please

The other version is "beaver" instead of "lion".

Yep,not most new under the sun about impregnation by an other "donor".