Chumley Huffington is a student at Duel Academy who initially belongs to the lowest-ranked dormitory, Slifer Red. He is a young man whose facial features, build, and hairstyle are deliberately designed to resemble a koala. Chumley was forced to retake his freshman year after failing his first attempt, which contributes to his initial lack of confidence. His time at the academy is marked by a significant personal journey, transforming from a struggling student into a respected card designer.

In terms of personality, Chumley is often portrayed as lazy, gluttonous, and averse to physical exertion, particularly running. He is a reluctant participant in dangerous situations, preferring comfort and his favorite food, grilled cheese sandwiches. Despite these unambitious tendencies, he is a deeply loyal and supportive friend who cares genuinely for the well-being of those close to him. His catchphrases in the English version of the show include declaring things as lischus, meaning delicious, or not lischus.

Chumley’s primary motivation is to find his own path and prove his worth, both to himself and to his father. He struggles with the fear of being a failure but is encouraged by his friends to gain more confidence. His role in the story is largely as a supportive sidekick to the main protagonist, Jaden Yuki. However, he has a pivotal character arc in the first year. His father, Mr. Huffington, believes Chumley is wasting his time at Duel Academy and wants him to leave to work in the family business. To settle the matter, they duel. Although Chumley duels valiantly, fusing Big Koala and Des Kangaroo to summon the powerful Master of Oz, he ultimately loses to his father’s unique Flipping the Table strategy. Despite the loss, Mr. Huffington is impressed by the skills his son has learned and the supportive friends he has made, allowing him to stay.

Later, Chumley enters a card-design contest and wins by creating the spell card Ayers Rock Sunrise. This achievement catches the attention of Maximillion Pegasus, the president of Industrial Illusions, who offers Chumley a job as a professional card designer. To ensure Chumley has earned the right to leave the academy for this opportunity, the strict instructor Dr. Vellian Crowler duels him in a final test. Chumley holds his own and even plays his self-created card, but he is defeated. Crowler, however, is impressed by how far Chumley has come in his studies and allows him to leave. Chumley returns later during the Genex Tournament alongside Pegasus to give Jaden a new card, Skyscraper 2 - Hero City, to aid him in a difficult duel.

Chumley’s key relationships are central to his development. His best friends, Jaden Yuki and Syrus Truesdale, are his biggest supporters. They encourage him to believe in himself, and they even give him key cards for his deck, including Master of Oz and Des Kangaroo. His father, Mr. Huffington, is an initial antagonist whose doubt Chumley seeks to overcome. Pegasus serves as his mentor and employer, recognizing his hidden talent for card design. His duel with Dr. Crowler serves as a final examination and a rite of passage that validates his growth.

Chumley is not a prominent duelist, participating in only two on-screen duels throughout the entire series. His notable abilities lie more in his unique talents than in his dueling win-loss record. He possesses a natural gift for creating cards, which ultimately becomes his true calling. In the original Japanese version of the anime, he has the latent ability to see and hear Duel Spirits, with the monster Des Koala acting as his unseen spirit partner; this detail is omitted from the English adaptation. His dueling style revolves around a Koala or Australian-themed deck, featuring cards like Des Koala, Des Kangaroo, Big Koala, and the fusion monster Master of Oz. His signature spell, Ayers Rock Sunrise, is a card of his own invention that becomes a symbol of his successful transition from student to professional card designer.