Levi-Strauss believed that narratives rely on binary opposites like hero/villain to help form plots. Todorov's theory proposes films follow five stages: equilibrium, disruption, recognition, attempt to repair, new equilibrium. Propp argued character functions structure folk tales, with roles like hero, villain, donor. Non-linear narratives can be cohesive like disruptive, non-sequential, or disjointed, or non-cohesive like ergodic, branching, or multi-linear.