Guy : Doctor, how come my gf is pregnant but I always use protection?!
Doctor : Let me tell you a story...
There was once a hunter who always carries a gun whenever he goes out hunting. One day, he took his umbrella instead of his gun and went out. A lion suddenly jumped in front of him. In order to scare the lion, the hunter used the umbrella like a gun and shot the lion. The lion died!
Boy : Nonsense!! Someone else must've shot the lion.
Doctor : Glad you understood the story!!