There was once a hat-seller who passed by a forest on his way back from the market. The weather was very hot and so he decided to take a nap under one of the trees, so he left his whole basket of hats by the side.
A few hours later, he woke up by some sounds. The next thing he realized was that all his hats was gone. He heard some monkeys on the tree and so he looked up. To his surprise, the tree was full of monkeys and they had taken all his hats.
The hat-seller sits down and think of how he can get the hats down. He think and think and start scratching his head. The next moment, he realized that the monkeys were doing the same action.
Next, he took down his own hat and saw the monkeys do exactly the same. An idea came to him, he took his hat and throw it on the floor and the monkeys do that too.
So he finally managed to get all his hats back.
Fifty years later, his grandson, Jack, also became a hat-seller and had heard this monkey story from his grandfather.
One day, just like his grandfather, he passed by the same forest, it was very hot, and he took a nap under the same tree and left the hats on the floor. He woke up and realized that all his hats were gone. He looked up and realized that the monkeys had taken all the hats. He remembered his grand father's words, started scratching his head and the monkeys follows.
He took down his hat and fanned himself and again the monkeys followed. Now, very convinced of his grandfather's idea, JACK threw his hat on the floor but to his surprise, the monkeys still hold on to all the hats.
Then one monkey climbed down the tree, grabbed the hat on the floor, gave him a slap and said "You think only you have a grandfather".