By setting Animal Farm on, uh, a farm, Orwell gets to play with our stereotypes about animals—well, expect he doesn't actually play with them so much as use them to his advantage. The pigs are smart and greedy, the horses are strong and loyal, the cat is lazy, the donkey is cynical and wise, and the humans—yeesh, the humans. They're just a mess.
Squealer can turn black to white. His language is fast, confusing, and convincing. You want to listen to Squealer because he makes you think that everything is okay. You're not really starving, your life isn't really made up of day after day of hard and unending labor, that moldy turnip is really some delicious cake.
Napoleon speaks as though his waste material smelled like the lovely aroma of roses. He knows he's the leader, and he won't let anyone forget it.
That about sums it up. The sheep just repeat the same phrase over and over again—they're stupid and easily manipulated. They probably watch cable news.