A Little Head?

A man walks into a bar and sees a well-decorated military officer sitting at the bar. He also notices that the man has a head about the size of an orange. So he walks up to the officer and says "That really is an impressive uniform, but I have to ask. What happened to your head?"

The officer replies "Well, about five years ago I was in a ship wreck and washed up to an island. When I woke I heard cries for help, so I went to investigate. I found a mermaid trapped under a rock. So I lifted the rock to free her, and she told me that she would grant me three wishes for my heroic deed. I wished that I could be sent back home, and she replied that she would grant that wish when the other two were made. I wished for tons of money, so she filled the island with cash, gold, and jewels as far as the eye could see. Next, I commented that I hadn't had sex for a while, and if she could do anything about it? She said 'Well, I have this fin in the way, I can't really help you with that.' So I said 'How about a little head?'"