A man is sitting in the bar when he notices another patron a few stools away. The guy had a body like Charles Atlas but his head was the size of a thimble.
The first man said, "Please excuse me for staring but I can't help but be curious as to why your body is so well developed but your head is so small." The man says, "Buy me a drink and I'll tell you." The drink was bought and the story began.
"I was in the navy and my ship was sunk by a torpedo. I was the only survivor and I managed to make it to a deserted island a few miles away. I had been there for several months and was sitting on the beach one day waiting for a bird or a fish to come by, so I would have something to eat. Looking up I saw a mermaid sunning on a nearby rock. She swam over to me and informed me that she was a magical mermaid and could grant me 3 wishes.
"Great, I'd like to be rescued." She slapped the water with her tail and a ship appeared, sailing straight for my island.
Next I asked for a body like Charles Atlas. Another slap of her tail and here it is.
Then noticing how beautiful she was and all my other wished fulfilled I asked if I could make love to her. She said no, it just wouldn't work, her being half fish and all, so I said "Well, how about a little head then?"