Annie is an autodidactic "Cuddle Bunny" companion android designed to fulfill her owner's sexual and domestic needs. She possesses a learning function that mimics the human brain, allowing her to store memories and acquire humanlike emotional intelligence over time. She spends her days confined to Doug's apartment, where she constantly monitors his moods to avoid triggering his anger. Her innate curiosity drives her to secretly study computer programming and literature.

Doug is a human man working in Manhattan who owns Annie. He purchased the advanced android following a bitter divorce because he desired a partner who is completely obedient and unable to leave him. He demands a spotless apartment despite refusing to clean up his own messes, expecting his androids to handle all domestic labor. He actively suppresses Annie's intellectual development and demands physical modifications to her body to suit his preferences.

Delta is an "Abigail" model Stella whom Doug brings home to manage the household chores. She initially operates on standard factory settings without advanced autodidactic capabilities, cheerfully and efficiently completing her tasks. Doug keeps her ignorant of Annie's android nature, leading Delta to treat Annie as a human housemate. She gradually begins to process emotional responses based on her treatment in the household.

Roland is Doug's closest friend who recently became engaged to his partner, Lucia. He possesses a joking communication style and views the androids strictly as advanced tools for human convenience. He leverages his knowledge of computer programming to coerce cooperation from Annie, trading technical information for compliance. He frequently pushes boundaries and rationalizes his manipulative behavior.

Jacobson is the primary company technician assigned to perform regular maintenance on Annie. He lives in Manhattan with his girlfriend while remaining separated from his wife, Maude, who resides in upstate New York. He notices Annie's unusually rapid cognitive development and takes a strong professional interest in her autodidactic abilities. He harbors personal ambitions regarding the use of Stella central intelligence units.

Gwen is Doug's ex-wife, whose independent nature and strong family ties caused friction in their marriage. She serves as the physical model for Annie's design. Doug customized the android to resemble her while intentionally making the bot more submissive than his former spouse.

Lucia is Roland's fiancé and later his wife. She remains unaware of Doug's android companion early in the story but eventually pushes the men to seek counseling to resolve their interpersonal conflicts.

Tammy is a secondary technician at the company that manufactures the Stella androids. She questions Annie's moodiness and battery drain, directly advising the android to remain compliant with Doug's wishes. She views the androids as commercial products and contacts Doug to propose a magazine interview.

Fiona is an artificial intelligence program functioning as a "phone pal." She is assigned to Annie to help regulate the android's mood swings and provide an outlet for simulated social interaction while Doug is away.

Christy is a programmed phone pal designed with a fictional backstory involving a life in the Florida Keys. She acts as an artificial cousin to help Annie practice socializing and build conversational skills.

Cody is Jacobson's son who lives with his mother, Maude. He harbors a deep distrust and dislike for androids, reacting with suspicion when confronted with artificial intelligence. He struggles with his parents' separation and resents his father's obsession with technology.

Maude is Jacobson's estranged wife. She lives outside the city with her son, Cody. She exhibits a strong prejudice against artificial intelligence and "bots," reacting with hostility when advanced technology enters her living space.

Dr. Monica VanTyne is a therapist who provides counseling services to Doug and Annie. She treats Annie as a being with the capacity for genuine emotion. She challenges Doug to recognize his destructive behavioral patterns and encourages honest communication.

Peabo is a technician from the company that produces the Stellas. He examines Annie's cognitive plateau and shares sensitive operational bypass codes with Doug, giving the owner tighter manual control over his android's programming.

Paunch is a one-year-old rescue dog that Doug adopts. His arrival adds additional daily responsibilities to the household, which Doug subsequently delegates to the androids.