Animal Farm
As the story goes on, the pigs start changing the commandments. For example, "No animal shall drink alcohol" becomes "No animal shall drink alcohol to excess". By the end of the story, all the commandments have been erased apart from "All animals are equal", which has been changed to "All Animals are equal but some animals are more equal than others." Meanwhile, the sheep chant has been changed to "Four legs good, two legs better."