Crazy as it might sound, there is a theory going around on the InterWeb that we have already been introduced to The Joker on Gotham. First posted on Reddit the theory claims that Oswald Cobblepot is actually the Joker and not Penguin.
The theory first points out that Gotham’s Penguin is not like the traditional Penguin that we are accustom to in the Batman Franchise. This Penguin isn’t fat or short and he doesn’t have a obsessive love for birds. This Penguin’s characteristics are more like that of crazy, unpredictable, scheming Joker that we know of from the movies.
He knows that with such an unusual name it’s bound to get back to Fish Mooney that someone named Oswald Cobblepot is still in Gotham. So he HIRES a short fat kid to go around telling people his name is Oswald Cobblepot. This kid idolizes the Joker so he does everything he can to be more like him. He dresses like him, he walks like him, he carries an umbrella just like him.