Poppy the mouse is the protagonist and hero of the novel. She and her family live under the oppressive rule of Mr. Ocax in the Dimwood Forest. Poppy’s objective during the novel is to discover his vulnerability at New House and rescue her family from his tyranny, and from the threat of starvation if they remain at Gray House. This goal informs her hero’s quest, motivating her to set off from home in Chapter 8. Her character arc in the novel reflects that of a classic hero in many ways.

The core themes of Poppy’s character arc align with many of the novel’s major themes. Along with the external conflicts she faces in Mr. Ocax and against the assumption of his authority in her family, Poppy’s most significant obstacle to growth is the fear she faces inside herself. Poppy begins the novel “timid” (3) in Chapter 1. While her boyfriend, Ragweed, is bold and flaunts defiance of Mr. Ocax’s rules, Poppy is fearful, although she resents herself for this cowardice (5). Ragweed’s death in Chapter 1 is a significant turning point for Poppy: At first, it causes her to reject The Importance of Challenging Assumptions, but ultimately reinforces her conviction to do so after she sees her family’s reactions to Ragweed’s death in Chapter 4.