Vladimir Propp was a Russian scholar who developed a theory of character types in narratives. He proposed that there are seven main character types that appear in stories: the hero, the villain, the donor, the princess, the helper, the princess' father, and the false hero. Each character type performs a specific narrative function, such as the hero embarking on a quest or the villain opposing the hero. However, critics argue that Propp's theory does not apply to all stories, as some narratives feature different or more complex character configurations than his proposed types.