The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which.
This is the last sentence that finishes the novel of George Orwell. The inhabitants of the farm decide to sneak to the windows of the former farmer’s house and see what pigs are doing there. They realize that pigs are selling alcohol to the human farmers from the neighboring farms - who they claimed were their sworn enemies and enemies of the animals. Moreover, the pigs now walk on two legs and dress up in farmer’s clothing. Their manners and behaviour become so similar to human that, when the quarrel between guests and pigs turns to a fight, the spectators can’t divide who is who in that fight.
The bitter irony Orwell puts into this line is addressed to the Communist Party leaders, who distorted their own ideals for their benefits. Communism (in the form of Seven Commandments given by Old Mayor) divided them from capitalists (humans). The animals wanted to go their own, separate way of development, because the human rulers were too oppressive for them. But gradually the pigs, who were more intelligent and skilled, became drunk with power over the more dim-witted animals. They tried to distort their own ideas here and there, slowly, to not alert the people, and finally they end up living in luxury and oppressing their own people as much as the previous ruler, oblivious to the peoples’ needs. The Communism is never built, but capitalism, in its most ugly form, returns, covered by the propaganda of beautiful ideas of equality. Behind the closed doors pigs turn into humans.