Lap Pinky

Of course I won't laugh," the doctor said. "I'm a professional.  In over twenty years I've never laughed at a patient."

"Okay then," Fred said, and proceeded to drop his trousers, revealing the tiniest penis the doctor had ever seen.
It couldn't have been the size of a peanut.  Unable to control himself, the doctor started giggling, then fell laughing to the floor.  Ten minutes later he was able to struggle to his feet and regain his composure.

"I'm so sorry, "Said the doctor, "I really am.....  I don't know what came over me.  On my honor as a doctor and a gentleman, I promise it won't happen again.  Now what seems to be the problem?"

"It's swollen," Fred replied.