In Boar’s Sister Junior, Boar welcomes Junior, her new and lively younger sister, into the Gee family. During a rainforest-like lunch, Boar and her mother find a stuffed toy bin where a small green gecko emerges—later named Gus Junior. As part of the family, Junior’s unique gecko abilities, like scaling heights and fast movement, initially spark Boar’s envy but soon turn into admiration.

Junior’s personality contrasts with Boar’s: she loves unicorn dresses while Boar prefers simple attire. However, Junior deeply idolizes her sister, mimicking her style and habits. Though Boar is frustrated by Junior’s clinginess, she ultimately embraces her role as a big sister, guiding Junior to slow down and understand her surroundings. Throughout Book Three, Boar grows into her new responsibilities, strengthening their bond in an endearing and heartfelt journey.