Rabbi Samson Raphael Hirsch (Shemos 7:28) wrote that the plague of frogs came to show the Egyptians that the management of creation is entirely in the hands of Hashem, and that everyone is insignificant before Him. For it is in the nature of frogs to flee from light and noise, especially from humans. Yet now they came to disturb the royal person in his bedroom and bed, and the king's servants and the people, entering their bodies and crawling on their bread, without any fear of them.