The Animals

Christopher Boone goes to a school for students with "special needs" because he has a form of autism. Although it is never definitively stated within the story which autistic spectrum condition Christopher has, the summary on the book's inside cover states it to be Asperger syndrome. Christopher is a mathematical savant, has a photographic memory, and is extremely observant. However, he has difficulty understanding human behaviour, gestures and relationships. He dreams of being an astronaut and takes a deep interest in mathematics. He owns a pet rat named Toby, which he feeds with food pellets.

Christopher has many traits that set him apart from others because of his perception of life. He is unable to recognise and comprehend facial expressions besides 'happy' and 'sad' and also has difficulty in understanding metaphors. He likes lists and facts, has a fear of strangers and new places, and his favourite dream is one in which everyone except people similar to him dies. In addition, he is over-sensitive to information and stimuli. For this reason, he screams and reacts violently to people who touch him. However, he doesn't mind pressing his fingers against those of his parents' as a gesture of love. He curls up and groans to protect himself against overwhelming noise or information.

Christopher hates the colours yellow and brown, but loves red. This extends to adding red food dye to brown- or yellow-coloured food (and being unable to eat two different kinds of food that are touching), and also his belief that seeing three, four or five red cars in a row means it's a "quite good", "good", or "super good" day respectively, while four yellow cars signify a "black" day. Finally, he dislikes eating food from new places and the furniture being moved.