If you look at the beginning of Chapter One carefully, you can see that a lot is suggested about each of the animals by the order in which they enter and the manner in which they enter. Major, the pig with a "wise and benevolent appearance" is there first, swiftly followed by the three dogs and other pigs, who settle themselves beneath the platform indicating their position of leadership and importance in the farm. The hens perch themselves on the window-sills, indicating that they are fringe players in what is going to happen, and the sheeps and cows significantly position themselves "behind the pigs."
Boxer and Clover show their care and concern for other animals by entering slowly and taking their time in case they accidentally crush another animal. They are followed by Muriel and Benjamin, then, after the ducklings enter, Mollie prances in, "mincing daintily," indicating her vanity and self-centredness, which is of course reinforced when she goes right to the front and shakes her white mane, trying to draw attention to the red ribbons. Lastly, the cat enters seeking a warm place where she can "purr contentedly" without listening to any of the following speech.
Thus we can see that the order in which the animals enter, the way they enter and where they position themselves gives us vital clues about their character and the kind of role they will play in the revolution that is to follow.