In Chapter Eight, it is revealed that Napoleon is no longer called by this name. Instead, he is given a very formal title, "our Leader, Comrade Napoleon." Moreover, the pigs invent additional names for him, like "Father of All Animals," "Terror of Mankind," "Protector of the Sheep-Fold," and "Ducklings' Friend."
These names are significant because they reveal much about Napoleon's character. Specifically, they show just how highly Napoleon values himself. He believes that he is the best person to lead the farm and, more importantly, he wants and expects the other animals to acknowledge this.
Moreover, by giving himself such a title, Napoleon also demonstrates his inflated sense of self. He knows that as the leader of the farm, he is set apart from the other animals. As such, by making the animals use this title, he shows that he wants these differences to be publicly acknowledged by everyone. It, therefore, shows that his self-worth is nothing short of total arrogance.
Finally, these titles suggest that Napoleon believes he is special. Specifically, that he is more than just a man; almost like God or another other deity. He, therefore, introduces these titles because he wants to be celebrated and revered, as proof of his special status.