Chester is a small, inch-long, shiny black cricket from the peaceful meadows of Connecticut. Accidentally transported to New York City, he feels frightened and out of place in the noisy urban environment. He possesses a natural talent for creating beautiful music by rubbing his wings together, which he uses to express his emotions. He has a gentle soul and a strong sense of integrity, taking responsibility for his actions when things go wrong.

Mario is a hardworking young boy who spends his summer vacation helping his parents run their struggling newsstand. He yearns for a pet and quickly adopts the lost cricket he discovers in the subway station. He acts as a gentle, compassionate caretaker who treats his new pet with respect and actively researches how to properly provide for him.

Tucker is a highly sociable, energetic mouse who lives in a drainpipe in the Times Square subway station. He prides himself on his street smarts, his ability to scrounge for food, and his life savings of dropped coins. Despite a slightly materialistic streak, Tucker possesses a generous heart and eagerly welcomes newcomers to his beloved city.

Harry is a large, tiger-striped cat with gray-green eyes who defies nature by living peacefully with a mouse. He moves silently through the city and possesses a calm, cultured personality. He appreciates the finer things in life, including chamber music and opera, and acts as a steadying presence for his more impulsive friends.

Papa Bellini is the tall, somewhat stooped patriarch of the Bellini family who built their newsstand by hand. He is a mild-mannered peacemaker who dislikes conflict and often mediates between his strict wife and his son. He maintains a quiet optimism about their struggling business and shares a deep passion for Italian opera.

Mama Bellini is a short, stout, and practical woman who worries constantly about her family's financial survival. She is fiercely protective of their livelihood and quick to blame outside factors when things go wrong. She views the world through a realistic, somewhat pessimistic lens, though she hides a softer side tied to her memories of Italy.

Mr. Smedley is a staid, dependable music teacher who is Papa Bellini's best and most cultured customer. He is highly educated in the musical arts and appreciates classical and operatic performances. He recognizes true talent when he hears it, displaying an enthusiastic reverence for natural musical gifts.

Sai Fong is an elderly Chinese gentleman who operates a cluttered novelty shop and hand laundry in Chinatown. He is knowledgeable about traditional Chinese folklore and cricket care, eagerly sharing his cultural heritage with visitors. He is welcoming and hospitable, viewing crickets as symbols of good luck and truth.

Paul is a kind subway conductor who drives the shuttle trains on the level of the Times Square station where the Bellinis' newsstand is located. He is friendly toward Mario and tries to support the struggling family business when he can.

Mickey is a red-haired counterman at a local restaurant near the newsstand. He is friendly and accommodating, humoring Mario's new pet by preparing a tiny water cup and a miniature ice cream soda for the insect.