There was once a boy whose parents were the custodians of an impressive old castle. The place was full of old paintings, arms and armour. One day, the boy noticed something strange about one of the main paintings. Normally, it showed one of the old kings, with sceptre in hand, standing next to his son and some members of the court. But the king had disappeared from the painting. The boy was very worried by this, and he thought he must have made some mistake; but a while later he walked past the painting once more, and noticed that the sceptre had been left there by the king, and was leaning over. The boy was intrigued. Even more so when, soon after, he saw that the angle of the sceptre had increased. At that rate, in a few hours it would end up hitting the prince on the head. So the boy started looking throughout the castle for the missing king. Finally, he found him in one of the castle bathrooms, quietly enjoying a wonderful bubble bath in the biggest bathtub in the whole building. The boy was speechless. On seeing his shock, the king explained to him that he had spent years and years hanging on the walls of that castle, and no one had cleaned the dust off him; not even once. He had gotten so dirty that he couldn't stand it a second more, and had had to run off to get a bath. When the boy had recovered from the surprise, he respectfully explained to the king what was about to happen with the sceptre and the prince. The king hurried out of the bath, to return to his place in the painting, thanking the boy for the warning, and begging him to ask his parents to clean the paintings every now and again. But the boy didn't need to ask his parents. From that day on, he himself cleaned and cared for all the paintings and sculptures in that castle, making sure that none of the figures would ever again have to escape to have a good bath. 
It's important to keep things clean. 