The mice are not universally good, nor are the pigs universally good or bad. Mice can pass for other animals by wearing pig masks or cat masks. The allegory falls apart at times when the animal-humans deal with actual animals, as when Art’s Jewish therapist has pet cats (!), or when Art and Françoise have to use bug spray to get rid of bugs when they are vacationing in the Catskills, a reference to Zyklon-B, the pesticide used to gas concentration camp prisoners.