Will is Jim's best friend, and at the beginning of the book he is much more of a thinker than his friend, who favors action. But as the story unfolds Will finds that, much like Charles Halloway, he is capable of quick and decisive action once he has made a critical decision. He saves Jim several times and saves his father another time because, although he is only a thirteen year old boy, he is certain of his knowledge and believes that he is doing the right thing. Will cares deeply about doing what is right, and, unlike Jim, he favors inaction when the alternative is harmful or destructive. Will is selfless, and he runs tremendous risks to save Jim even when Jim himself does not necessarily want to be saved.
Jim is in turmoil throughout the course of the book. He wants to help Will and Mr. Halloway fight the carnival but at the same time he is filled with desire to ride the carousel and instantly grow up. Jim is fiercely independent and afraid of nothing, and with the carnival these traits threaten to get him into a situation that as a thirteen year old he will not be able to get out of. Fortunately, he has Will and Mr. Halloway to help him. Jim is not sure of what he wants, and he is the type who tries thinks if he thinks he might like them. But the carousel is not the sort of thing that one can just try and then walk away from. Jim knows this but refuses to admit it because he is so intent on going for a ride.
Charles Halloway finds himself throughout the course of the novel. He has to protect Will and Jim, and in the process he is transformed. Mr. Halloway starts out as an old man who vividly remembers his times as a youth but is sure that his days of action are over. But he slowly learns that there is more action in him then he thought, and it also becomes apparent that he is a man with cool nerves and much inner strength. He is the only one who truly sees the carnival for the mockery that it is, and this allows him to laugh at it. He destroys the carnival by laughing at it, and he laughs with such certainty because he is completely comfortable with who he is.
The major evil character in the book, Mr. Dark is the Illustrated Man. He is covered in tattoos and each tattoo allows him to exert some power over the figure that is represented. He feeds on pain and destruction and wants nothing less. Mr. Dark is afraid of nothing except the good that Charles Halloway uses to defeat him. He is tremendously strong and intimidates people, inspiring fear when he wishes to. The freaks at the carnival are completely within his power, and he uses both manipulation and force to bend people to his will.
Along with Mr. Dark, Mr. Cooger is in charge of the carnival. He is pure evil, and he pretends to be Miss Foley's nephew Robert in order to get her to ride on the carousel. Mr. Cooger also tries to get Jim to ride on the merry-go-round, and if not for Will he would have succeeded. Although he is dangerous and cunning, Mr. Cooger is a threatening possibility for most of the book since he is too old to do anything after Will messes up his carousel ride.
A woman who is not happy with her life, Miss Foley thinks that she can find happiness on the merry-go-round. She is obsessed with the idea of the carousel and tries to get Will and Jim into trouble so that they will not stop her from using it, even though the boys saved her from the Mirror Maze. The carousel does not save her but rather takes everything from her and turns her into the broken little girl that the boys come across.
Though the Witch is blind, she feels and hears things that no one else feels or hears. She is the lookout for Mr. Dark and the carnival. The Witch is evil and greedy, and Will uses those traits against her when he destroys her balloon. She is also fearsome, but only if her powers are believed in, and Charles Halloway destroys her with a laugh.
In the first scene Mr. Fury warns Will and Jim of the storm that is coming. It turns out that he is the first casualty of the carnival because he cannot resist the beauty of the ice sculpture in the store. Once he is turned into the Dwarf, his presence is a constant reminder of the evil of the carnival and the horrific damage that is inflicted upon its victims.
In the one scene where Jim talks to his mother much of her character comes through. She is a single mother. Jim's father beat her and has been gone for many years, but she is still fragile. She lost her other two children and now has only Jim. She tries to protect him but knows that he will leave her someday.
A very minor character in the book, present mostly in Will's thoughts, his mother is truly happy and content in her life. Will and Mr. Halloway deliberately protect her from the carnival by not telling her what is happening.
The barber, Mr. Crosetti informs Will and Jim that he smells cotton candy. He realizes that a carnival is coming to town and he becomes sentimental. Mr. Crosetti was likely one of the first casualties of the carnival because the next night a sign in his shop says he is closed due to illness.
The owner of the United Cigar Store, Mr. Tetley sees Will and Jim in the beginning of the book and pops up throughout the story. His significance is solely due to the fact that he is the proprietor of the store.
Robert is the name of Miss Foley's real nephew who never appears in the book. When Will and Jim first see Miss Foley at the carnival she is looking for him, and later Mr. Cooger pretends to be him.