There is a midrash about the second plague: that it began with only one frog. A very big one! But just one. The Egyptians attacked it and with each hit burst out the multitudes of frogs that then smothered the country. One commentary is this is what happens when you get angered and go on an attack which only escalates the situation. I want to offer another interpretation. All the plagues were alarm calls for the Egyptians and their leadership to abandon slavery, and their ignorance and superstitions, and to the wonder of Hashem. The plagues were all supernatural occurrences. So, the appearance of one gigantic frog might be such a wake-up call, but they didn’t see or listen, they just attacked to preserve their own blind corruption. They couldn’t perceive the miracle in front of them. A wonder and a warning.