Doctor

"How do you account for this?" he asked the brothers.

"It's hereditary, sir," the older one replied.

"I see," said the doctor, writing in his file. "Your father's the reason for your elongated penises?"

"No sir, our mother."

"Your mother? You idiot, women don't have penises!"

"I know, sir," replied the recruit, "but she only had one arm, and when it came to getting us out of the bathtub, she had to manage as best she could."