Stuart is the protagonist of the story—the person whose actions and decisions drive the narrative. The protagonist is often, though not always, the viewpoint character of a story, and is typically the character with whom readers are meant to form the closest attachment. As the titular character, readers follow Stuart’s adventures and get to know him best out of all the characters in the book.

Antagonists present conflict for protagonists and prevent them from reaching their goals or living their lives. Stuart encounters two kinds of antagonists. The first is Snowbell, a household “villain” whose actions negatively affect Stuart’s life. Snowbell goads Stuart into showing off and proving his strength; when Stuart ends up stuck in the window shade, Snowbell plants his items next to the mousehole to trick the Littles into thinking Stuart escaped into the household mousehole. Snowbell also attempts to attack Margalo, Stuart’s first friend, while she sleeps; this drives Stuart to defend her, and he heroically shoots Snowbell’s ear with his bow and arrow, “defeating” the villain.

The second kind of antagonists Stuart confronts are inanimate forces and untoward events. The storm on the water during the sailboat race is one example; being dumped into a garbage truck is another.