Jimmy and Jack were twins, but they weren't identical - far from it. They looked like the before and after photos in those old body-building adverts. Jimmy was a skinny thing, while Jack was well-built and muscular. As a result, Jack seemed to attract women without making an effort - everywhere he went they would cluster round him, while poor Jimmy struggled and even when women approached him - usually because he was standing next to Jack - he found it difficult to talk to them.
However the two were the best of friends and Jack always did his best to help Jimmy out, though it was rarely successful. One day the two planned to go to the beach. Jack knew that as soon as he stepped onto the sands, wearing his swimming trunks, the women would come flocking and hopefully Jimmy would benefit from the overflow, so to speak. Unfortunately as they were about to set off something cropped up and Jack found he had some business to take care of first. He said to Jimmy, "You go on ahead and I'll meet you there. But in the meantime we need to do something to give you an advantage. That skinny body is what's holding you back. We can't give you muscles but we can make you look a bit more of a stud - get a potato and pop it down your swimming trunks and you'll look a bit more macho."
Jimmy set off and Jack took care of his business, then headed for the beach to find his brother. It didn't take long: though the beach was crowded there was a large circular gap at one point, as if people were trying to keep away from some unpleasant object. Right at the centre sat Jimmy, looking miserable. He got to his feet as Jack approached.
"This is all your fault," he said. "I did what you told me - I got a potato and stuck it down my swimming trunks, but as soon as I came out of the changing rooms people started screaming and running away. You said it would attract the girls but nobody will come within twenty yards of me!"
"I'm not surprised," said Jack. "You were supposed to put the potato down the front of your trunks!"