12 inches
A man with a stuttering problem tries everything he can to stop stuttering, but he can't.
Finally, he goes to a world renowned doctor for help. The doctor examines him and says "I've found your problem.
Your penis is 12 inches long. It weighs so much it is pulling on your lungs, causing you to stutter."
So the man asks, "What's he cure, doctor?".
To which the doctor replies, "We have to cut off 6 inches." The man thinks about it, and eager to cure his stuttering, agrees to the operation. The operation is a success, and he stops stuttering.
Two months later he calls the doctor and tells him that since he had the 6 inches cut off, all of his girlfriends have dumped him, and his love life has gone down the tubes.
He wants the doctor to operate to put back the six inches. Not hearing anything on the line, he repeats himself, "Hey doc, didn't you hear me? I want my 6 inches back!"
Finally, the doctor responds, "F-f-f-f-f-f-#ck Y-y-you!