The only animals who didn't change over the years was who in animal farm?

In George Orwell's "Animal Farm," the only animals who do not change significantly over the years are the sheep. They blindly follow the pigs and repeat slogans like "Four legs good, two legs bad," without questioning the evolving circumstances on the farm. This symbolizes the unthinking masses that can be easily manipulated by those in power, reflecting a critique of passive acceptance in society.