"Who Moved My Cheese?" is a short parable that uses the characters Sniff, Scurry, Hem, and Haw to represent different reactions to change. Sniff and Scurry, the mice, adapt easily, while Hem and Haw, the Little people, struggle with denial and fear. The book explores how to overcome these difficulties and embrace change, using the metaphor of "Cheese" as a representation of what you want in life. The excerpt further highlights the story's practical application through a discussion among former classmates who relate their own experiences to the characters, illustrating how the parable can be applied in both personal and professional contexts.