When the pigs realize how incredibly gullible the other animals are, it becomes difficult for them not to take advantage of it, especially after Napoleon's rise, when the honorable pigs are chased off or killed. The pigs move into Farmer Jones's house so they can "think" better in the peace and quiet. They decide they can get up later in the morning than the other animals. With the dogs to protect them, more and more they abandon any pretense of living like the others. Privileges they assume include drinking alcohol, trading with humans, wearing green ribbons in their tails on Sunday, avoiding manual labor, and eating well while the other animals are hungry. Their children are schooled separately and the other animals are told they must stand aside when they meet a pig on the path. They move from a willingness to lie to a hardening of heart and conscience. They show their complete corruption when they sell poor faithful Boxer to the glue factory and use what they get from his body, the body of the horse who loyally sacrificed everything for them, for a drunken revel. Finally, the pigs stand on two legs, wear full sets of clothes, and carry whips in their trotters. They have turned into their human masters and have no feelings left for their fellow animals. 

Throughout the book, the pigs steadily accrue more privileges, despite their outward claims that they sacrifice as much, more even, than the other animals. They appropriate  the apples for their mash early in the revolution, begin sleeping on sheets, take up residence in the farmhouse, and eventually take to wearing human clothes and walking around on two legs. The degree to which they have corrupted the ideals of the revolution is reflected in their changing the Commandments to read: "ALL ANIMALS ARE EQUAL BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS." By the end of the book, they have drifted so far from the ideals of the revolution that the other animals cannot tell the physical difference between them and the humans.