His speech about the evils perpetrated by humans rouses the animals into rebelling. His philosophy concerning the tyranny of Man is named Animalism by his followers.
Old Major
He becomes one of the rebellion's valuable leaders. After drawing complicated plans for the construction of a windmill, he is chased off of the farm forever by Napoleon's dogs and thereafter used as a scapegoat for the animals' troubles.
Snowball
He's one of the leaders during the rebellion against Jones. After the rebellion's success, he systematically begins to control all aspects of the farm until he is an undisputed tyrant.
Napoleon