What impact did the character Napoleon from the book Animal Farm have on the other characters? What was his impact on the plot of the story?

Napoleon is an interesting character because he is one of the smartest pigs on the farm. In fact, at first we don't see too much of an impact from him, especially with regards to the initial conflict and subsequent rebellion by the farm animals. It is only after the rebellion that he steps up to take a leadership role over the other animals. In the book, he is described as fierce-looking, with a reputation for getting his way. The other animals know that he will eventually get what he wants, so they don't put up too much of a fight. In this way, he has a powerful effect on them; one might say that he has a manipulative effect on them.

Everything that Napoleon doesn't want to deal with, he finds a sneaky, yet effective, solution for and bides his time until he is able to solve the problem for himself. He does this by raising dogs in order to chase Snowball off of the farm. He never has to speak for himself, because Squealer does it for him. In this way, he can avoid taking responsibility. Napoleon also does away with public meetings in order to avoid protests, and he appoints himself as the head of every single committee, so there's no disagreement. Because of this, he effectively succeeds in silencing the other characters. 

In order to appear more powerful, he spends most of his time separated from the others, surrounded by a pack of dogs which serve as his protectors. This gives him the image of being all-powerful, mysterious, and not someone that you want to mess with. He changes the story by forcing a few of the other animals to make false claims in public. Essentially, he rewrites history to suit his own needs. Just like Stalin, he claims to be doing it all for the good of everyone, but he is really just motivated by power and greed.