Like all books, "Animal Farm", the book, is different from "Animal Farm", the movie. One of the reasons is the characters. Some of the characters that were in the book were not in the movie. Those were characters like Mr. Whymper, Clover, and Mollie (who was only shown in part of the movie). In the movie, Jessie, the dog that was only mentioned in the first chapter, replaced Clover. Jessie narrated the story, was the main character, and was in the story the entire time.
Some of the events that were in the book were not shown or did not happen in the movie. These were events like the bank note forgeries and some of the things that Squealer said to them like how he convinced them to let the pigs use the apples and milk in their mash. They did not even mention this event in the story.
Other things that they did not even mention in the movie were the Sunday meetings and something they didn't mention in the book was Napoleon's addiction to whiskey. One of the main events in the book that were not shown in the movie was the battle where Boxer split his hoof. The only two battles that happened were the Rebellion and the Battle of Cowshed. One event that happened in the movie that did not happen in the book was when Squealer took Jones' camera equipment and used it to speak to the animals.
Another different thing about the story was when the events took place. They showed the pigs walking on their hind legs after they showed when Jessie couldn't tell the difference between the humans and the pigs. One of the last things that were different about the movie was the ending. It didn't end...