Why frogs?

 And I saw three unclean spirits like frogs come out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet. Revelation 16:13

"Why frogs, of all things?

The background of Revelation 16 is thoroughly grounded in the plagues against ancient Egypt just before the Exodus. One of those plagues consisted of an overabundance of frogs. But of all the plagues that fell on Egypt, why would frogs be mentioned at this point?

When Moses first came in to Pharaoh, his God-given authority was demonstrated when his brother, Aaron, threw down his walking stick and it became a snake (Ex. 7:8-10). But Pharaoh's magicians weren't worried. They threw down their walking sticks, and they became snakes also (verses 11, 12).

Then Moses and Aaron went out and turned the waters of the Nile into blood (verses 14-21). Again Pharaoh's magicians were able to counterfeit that miracle (verses 22, 23).

Next Moses and Aaron struck Egypt with a plague of frogs (Ex. 8:1-6). And again Pharaoh's magicians were able to duplicate the feat (Ex. 8:7).

But as it turned out, the plague of frogs was the last that Pharaoh's magicians were able to duplicate (Ex. 7:18, 19). 

The frogs, therefore, constituted the last deception of the Exodus.

---That is why there are frogs in Revelation 16:13. 

---They signal that the message of Revelation 16 has to do with the last deception of earth's history.

Revelation 16:14 says that these frogs are "spirits of demons." They are the demonic counterparts of the three good angels of Revelation 14:6-12. Both groups of angels have a mission to the whole world (Rev. 14:6; 16:14), one trio calling the world to worship God, and the other gathering the people of the world into the service of the unholy trinity. "They are the spirits of demons performing miraculous signs, and they go out to the kings of the whole world, to gather them for the battle on the great day of God Almighty" (Rev. 16:14)."
Jon Paulien