Meg is a gifted mathematician, but her very high intelligence interferes with her school performance. She struggles to follow rules, and resists authority figures. Meg is stubborn, impatient, and can't help expressing her emotions. She considers herself unattractive and clumsy, and she wears glasses and braces. She loves her family and is fiercely devoted to them. Meg develops maturity, self-confidence, and independence through the events in the book. She realizes her faults can be her strengths.
Charles Wallace is insightful and clever, and possesses wisdom far beyond his years. He has an uncanny understanding of math and science, and his mind reading skills give him exceptional knowledge of human behavior. He is particularly close to his mother and sister, Meg. Despite his intelligence, Charles Wallace cannot read and doesn't attend school. He deliberately hides his intellect so people in town consider him "dumb." Charles Wallace is well aware of his gifts, and can sometimes be arrogant, and overestimate his own abilities.
Calvin is outgoing and friendly, and has a gift for communicating with all kinds of people. He enjoys English and reading but struggles in math. Despite his popularity in school, Calvin secretly feels alone and longs to be accepted. He acts a certain way to fit in with others, but this behavior doesn't reflect his true self. His large family ignores him, and he envies the close Murry family. Calvin and Meg realize they have more in common than they thought and become romantically interested in each other.
Mrs Whatsit is wise and good-natured. Although she is around two billion years old, she is the youngest of the children's three guides. Her relative youth allows her to communicate in a way the children understand. She can adopt different physical forms, including the form of a magnificent winged horse. Mrs Whatsit was once a star who died in an explosion, or supernova, and her true nature is "beyond human understanding."
Mrs Who is well read and speaks multiple languages. She finds it challenging to verbalize her own thoughts, since she sees language as an imperfect medium of communication. Before the children embark on a dangerous mission, Mrs Who gives them literary quotes to inspire, motivate, and empower them. She also gives Meg a pair of glasses to help rescue her father.
Mrs Which is the eldest of the three guides and has the most experience in tessering, or time traveling. Because of her physical distance from the children, her words sound as if she is coming from far away. Mrs Which enjoys playing practical jokes to entertain Mrs Whatsit and Mrs Who, and likes dressing up as a witch. However, she takes her responsibilities seriously.
IT functions as a symbol of conformity and control. The large brain rules a planet like a totalitarian leader, allowing its residents no freedom. The power of IT also shows the consequences of the brain ruling without a heart. IT is physically repulsive, gives off bright red light, and has a loud, rhythmic pulse that drowns out independent thought.