Mickey is a member of The Terces Society, and is one of the most minor characters in the series. He is a clown at the circus and his best friend is Morry, another member of the secret society. Mickey is never mentioned much, and he usually has nothing to do with the plot of the story. He is mostly included to add members to the society to which he belongs. The clowns on the cover of "This Book Is Not Good For You" could be Mickey and Morry, but we don't know for sure. In fact, we know very little about the clowns.