What are ' Cooties'?

Question: What are “cooties”? I watch “Arthur,” the cartoon (show with animation (drawings)), every morning, and the characters often say, “You have cooties!” but I do not understand! Please help!

Answer: Cooties are imaginary (not real) germs. Germs are the very, very small living things that we can’t see, but that can cause disease or illness. To insult (to treat with disrespect) someone, you could say that they have cooties. Children like to say this to people they don’t like. Like the word “germs,” we nearly always use “cooties” as a plural noun, almost never as a singular noun. Adults don’t usually use the word “cooties” unless they were trying to be funny.