Stella is a third-grade Mexican American girl living in Chicago. She frequently struggles with speaking, confusing Spanish and English pronunciations, and takes specialized speech lessons. She feels self-conscious about her accent and her status as a resident alien, but she has a deep passion for art, writing, and marine biology.

Stella's mother is a single parent who works full-time at a radio station. She moved her family from Mexico City to Chicago when Stella was a baby. She actively exposes her children to their Mexican heritage through traditional food, stories, and salsa music, prioritizing their well-being above her own stress.

Nick is Stella's eighth-grade older brother. He speaks Spanish comfortably, having spent more time in Mexico before the family relocated to Chicago. He acts as a mentor and protector for his younger sister, helping her with schoolwork while still engaging in typical sibling teasing.

Jessica is a popular student in Stella's class. She comes from a financially comfortable family that owns a horse. She targets Stella with cruel nicknames like "Stella Stares" and mocks her for being quiet and having an accent.

Jenny is a Vietnamese American girl and Stella's best friend. Placed in a different third-grade class this year, she makes friends easily, which initially causes Stella to fear losing her. She frequently trades food with Stella at lunch and offers practical advice on how to talk to new people.

Stanley is a new student who recently moved to Chicago from Texas. Despite his light features, he speaks Spanish, which surprises Stella. He is outgoing, confident, and attempts to build friendships by offering cookies to his classmates.

Stella's father lives in Colorado and rarely visits his children in Chicago. He frequently sends ill-fitting clothes from his brother's store as gifts and does not consistently pay child support, though he claims he would do anything for his kids.

Anna is a student in Jenny's class. She begins sitting with Jenny and Stella at lunch, proving to be kind and helping Stella feel more comfortable expanding her social circle.

Bridget is a student in Stella's class. She acts as Jessica's sidekick, echoing her cruel comments and laughing at Stella's expense.

Aunt Juanis is Stella's aunt. She travels from Mexico City to Chicago to spend the holidays with the family. She speaks only Spanish and occasionally interrupts Stella's attempts to speak it, but connects with her niece over art and music.

Stella's grandfather is a former radio performer who visits from Mexico. He is patient with Stella when she tries to speak Spanish and enjoys sharing music with the family.

Lauren is a student who befriends Stella and Jenny. She sits with them in the cafeteria and helps them ignore Jessica's bullying.

Isabel is Anna's best friend. She joins the girls' lunch table and friend group at school events.

Ms. Bell is Stella's third-grade teacher. She wears bright patterns, reads aloud to the class daily, and assigns the major animal research presentation.

Ms. Thompson is the school speech therapist. She works with Stella to correct her English pronunciation, focusing specifically on the "V" and "B" sounds.

Ms. Morales is the lively, Spanish-speaking school librarian. She wears bright outfits, keeps a stuffed goose on her desk, and introduces Stella to books about marine life.

Ms. Le is Jenny's mother. An immigrant from Vietnam, she works long hours and night shifts as a single mother to support her daughter.

Don is the school custodian. He immigrated to the United States from the Philippines and cries tears of joy while sharing his naturalization journey with the students.

Jason is Nick's friend. He tags along with the Diaz family during their special outing to the themed restaurant and arcade.

Pancho is Stella's pet betta fish. Because betta fish are naturally territorial and must live alone, Stella frequently compares her own feelings of social isolation to his life in the tank.