Who calls a meeting of the animals in Orwell's Animal Farm?
Animal Farm is an allegory. An allegory is a story that can be read on two different levels and the characters usually represent something else. Since the novel is an allegory of the Russian Revolution, many of the animals (and the farmer) personify real personalities in the revolution. For example, Snowball is an obvious reference to Trotsky, who was exiled from Russia in the early 1920's, Napoleon is the dictator Stalin, Boxer represents the Russian working class and the farmer is Czar Nicholas II.
Old Major is the farm's "prize Middle White boar." He calls the initial meeting of the animals in the opening chapter. He is probably a reference to Vladimir Lenin, the leader and chief theorist of Bolshevik doctrine in Russia. Old Major could also be the German philosopher Karl Marx. Marx formulated the communist philosophy in his treatise The Communist Manifesto.
Old Major calls a meeting of all the animals on Manor Farm to announce his theory of what would later be termed "animalism," and encourage them to rebel against Farmer Jones. He argues that the animals live miserable lives and that, even though Farmer Jones produces nothing, he reaps the benefits of the animal's labor. He urges the animals to overthrow the farmer and begin to take advantage of their own labor.
Just as Marx and Lenin did for the Russian Revolution, Old Major sets the tenets of the rebellion. He has several rules or "commandments" which he recites including, "All animals are equal." The pigs eventually quantify these doctrines and post them for the animals to see. Eventually, however, each rule is broken by the pigs and eliminated from the list, which winds up with only one commandment reflecting the pigs' dominance:
ALL ANIMALS ARE EQUAL
BUT SOME ANIMALS ARE MORE EQUAL THAN OTHERS