Ralph is a small, brown mouse living in the Mountain View Inn. He owns a prized mouse-sized red motorcycle given to him by a previous hotel guest. Caught between the cautious older generation of mice and his demanding younger relatives, he feels misunderstood and craves independence. He is brave but frequently struggles with his anxiety when faced with the dangers of the outside world.

Garf is a medium-sized boy wearing jeans and cowboy boots who is reluctantly headed to Happy Acres Summer Camp. He feels misunderstood by his parents and actively avoids connecting with the other campers. He craves space and time to be himself without the constant supervision of organized activities.

Catso is the predatory camp tomcat at Happy Acres. He roams the grounds looking for prey and views smaller animals entirely as toys or food. He is opportunistic and constantly looks for ways to breach the craft shop screen door to reach the caged pets.

Chum is a golden hamster with tan and white fur who considers himself a philosopher. He enjoys his comfortable life in captivity and spends hours running on his exercise wheel while thinking about the world. Having accepted his lack of freedom, he acts as an experienced voice of reason regarding the realities of being a pet.

Aunt Jill is a plump, cheerful head counselor at Happy Acres Camp. She demonstrates an impressive ability to look beyond obvious behavior to find the root of a camper's struggles. She approaches discipline by listening and offering constructive alternatives rather than strict punishment.

Karen is a twelve- or thirteen-year-old girl with long blond hair attending Happy Acres Camp. She actively participates in camp activities, such as making piggy banks from bleach bottles. She owns a ticking watch that becomes a central point of conflict at the camp.

Lana is a young camper at Happy Acres who possesses an unlimited affection for animals. She brings her pet hamster to camp every year and readily dotes on the local wildlife, including the dangerous camp tomcat.

Matt is the older bellboy and handyman at the Mountain View Inn. He is observant and empathetic, easily coaxing a smile from a grumpy Garf upon arrival. He respects Ralph's desire for independence and treats the young mouse like an equal, offering him firm but valuable advice about self-reliance.

Uncle Lester is an older mouse living in the Mountain View Inn. He represents the cautious, traditional generation of mice who prioritize safety and community sharing over individual thrills. He views Ralph's nighttime adventures as risky and completely selfish behavior.

Ralph's mother is a cautious mouse residing in the hotel. She worries constantly about the dangers of the human world and fears that Ralph will fall in with bad companions. Her protective instincts regularly manifest as controlling rules that frustrate her son.

Sam is the brown guard dog responsible for the safety of Happy Acres Camp. He takes his duties seriously and strictly monitors who enters the grounds. Despite his intimidating size, he possesses a strong sense of justice and duty toward the animals under his jurisdiction.

Garf's father is a practical man who stops at the hotel on the way to dropping his son off at summer camp. He expects his son to have a positive attitude and struggles to understand why Garf is resistant to organized recreational activities.

Garf's mother is traveling to drop her son off at summer camp. Like her husband, she dismisses Garf's anxieties about camp and insists that he will have fun. She fails to recognize his need for quiet independence.