Consistency implies that a literary character cannot have contradictory traits. Neither can characters behave in a manner incompatible with what has already been revealed about them, in description, actions, or the narrator’s comments. Normally we place a higher demand for consistency on literary characters than on real people. Since children’s literature is generally didactic, we place still higher demands for consistency on children’s literature characters. Characters must be understood from the text alone; therefore, any radical deviation in the way a character is presented will be perceived by readers as an artistic flaw.
– Maria Nikolajeva, The Rhetoric Of Character In Children’s Literature