Olive is the secondary protagonist of the novel. She is 11 years old and usually lives in Maine with her mother. Her dad passed away in a car accident and her mother has a new boyfriend who does not seem to like Olive. During the events of the novel, Olive is spending the summer in Hilton Head, South Carolina with her grandmother, Norma, with whom she is not particularly close. 

Olive wears daisy barrettes and overalls and carries around a picture of her dad in her pocket. She is energetic, curious, and deeply passionate about animals, often rattling off facts to anyone who will listen. Her enthusiasm is undercut by self-doubt: Her mother’s boyfriend, Frank told her she was “socially unprepared” for the real world and she struggles with the feeling that she is weird or embarrassing. This insecurity holds her back, preventing her from fully connecting with other kids, such as her peers in the Girl Scouts. 

Despite her self-consciousness, Olive is capable, intelligent, and driven. She helps her grandmother at the aquarium, where her knowledge and love for animals are accepted and supported. Olive is highly empathetic. She risks her life to save Leonard during the storm and cares for him unconditionally despite his mistakes. Olive does not judge Leonard and accepts him even after finding out his secret alien identity. She immediately prioritizes his well-being and looks for ways to include him in all the human experiences he hoped to have on Earth. Throughout the novel and because of her deep relationship with Leonard, Olive grows to see the goodness in herself as well.

Norma is Olive’s tough and no-nonsense grandmother. She has white hair and wears shirts and vests with many practical pockets. At the start of the novel, she and Olive do not have much of a relationship, as Olive only visited intermittently as a child. A longtime captain of a shrimping boat, Norma is hardened by years at sea, where she learned to be intrepid and efficient. She calls people “sailor.” 

Beneath her tough exterior, Norma is still grieving the loss of her son. The decline of the shrimping industry forced her to pivot to running the local aquarium, where she applies the same hardworking, no-nonsense attitude. Despite her gruffness, she has a deep love for the animals in her care, particularly the sea turtles. She has a close relationship with Q, her employee, and he recognizes her emotionally vulnerability. 

Over the course of the novel, Norma and Olive develop a deeper bond through their experiences looking after the animals at the aquarium and taking care of Leonard. Though Olive and Q worry that Norma will struggle with the shock of Leonard’s alien identity, she reveals that she is just as accepting and loyal to this unusual family as Olive is. By the end, she offers Olive a sign of their newfound closeness by telling her she can call her “Gran.”

Q is a quirky and upbeat employee at the aquarium. He wears colorful Hawaiian shirts and gives people he likes cheerful, hyperbolic epithets like Leonard, “king of cats” (134). From the start, Q is one of Olive’s biggest supporters, constantly affirming that she isn’t weird—she’s unique, capable, and she marches to the beat of her own drum. 

Q is also the first person after Olive to learn of Leonard’s identity. Q believes in aliens and is unfazed by the strangeness of Leonard’s situation. Q immediately offers to help get Leonard to Yellowstone and strategizes with Olive to convince Norma to accompany them on a road trip in Q’s motor home. By the end of the novel, Q has become more than just a friend—he is a part of Olive and Leonard’s found family.

Olive’s mom is mostly unseen in the present action of narrative, interacting with Olive through letters and phone calls with Norma. Olive’s mom is loving and supportive; she acknowledges Olive’s love of animals and looks for post cards that Olive will enjoy. She misses and cares for Olive but spends the summer with her boyfriend, Frank, traveling and exploring a potential move to California. Though she loves Olive, she is not completely aware of the tension between Olive and Frank, as Olive struggles to tell her mom what Frank said. At the end of the novel, Olive’s mom remains committed to the family, parting with Frank and accepting Leonard.

Frank is Olive’s mother’s boyfriend and serves as an unseen antagonist in the novel. His dismissive attitude toward Olive’s interests leaves a lasting impact on her self-esteem. By suggesting that she is weird and socially inept, he plants the idea in Olive’s mind that she is embarrassing and unworthy. This internalized insecurity shapes the way Olive sees herself, making her hesitant to open up to others. Frank makes Olive feel ashamed of her love of animals—the one interest that allows Olive to feel connected to her deceased father.