María is a teenage girl who leaves her mother in Puerto Rico to live with her father in New York City. She hopes the mainland United States will offer better opportunities for college and a professional career. She observes the different cultures in her school and apartment building carefully, capturing her experiences through poems, letters, and prose in English, Spanish, and Spanglish. Her intense focus on language helps her process her feelings of isolation.

Papi is a New York-born Puerto Rican who works as the superintendent for his apartment building. He left the island due to severe clinical depression and now masks his emotional struggles behind a strong, hyper-masculine persona. He fixes things around the building and performs older island songs for his neighbors at weekend rent parties.

Mami is an elegant English teacher living and working in Puerto Rico. She chooses to stay on the island rather than move to the mainland United States. She maintains her bond with her daughter through frequent, articulate letters detailing her life and thoughts.

Whoopee is a creative, highly expressive teenager who acts as a crucial emotional support system in her neighborhood. She speaks primarily in Spanglish and confidently stands up for others, including intervening when a neighbor mistreats a child. Despite her fearless attitude, she harbors a deep fear of her own reflection due to the lack of dark-skinned Puerto Rican beauty standards in popular culture.

Uma is a teenage immigrant from India living in the same apartment building as the protagonist. She exchanges facts about her home country for help studying for the United States citizenship test. She provides an important point of connection for the other teenagers in the building who feel marginalized by American beauty standards.

Abuela is a proud resident of Puerto Rico who travels to New York for a winter visit. She strongly prefers the idyllic climate of the island over the cold environment of the city. She keeps a detailed journal and engages in persistent, philosophical debates about the merits of island life versus mainland existence.

Ricky is a young man living in the apartment building who holds the neighborhood reputation of a "papi-lindo" — a highly attractive and overtly masculine boy. He uses his physical appeal to charm the young women around him, often leaving them heartbroken. His manipulative behavior creates friction among the teenagers in the building.

Mr. Golden is an English teacher at the local school. He actively supports his students' creative expression and validates their cultural identities. He sits in the back of the classroom singing along to student raps and provides crucial encouragement to young writers finding their voices.

Doña Segura is an elderly seamstress who creates beautiful embroidered patterns for her neighbors on special occasions. She crafts a treasured pillowcase featuring a sun over the ocean, providing a tangible connection to the island for her younger neighbors.

Señorita Stuckey is a white Spanish teacher whose curriculum relies heavily on exoticizing the countries she visits. She focuses entirely on tourist destinations rather than the people who actually live in Spanish-speaking regions.

Ms. Coronado is a science teacher who awkwardly attempts to defuse classroom racism. When a student makes a xenophobic comment, she volunteers to put a strand of hair under the microscope to smooth things over. Her well-intentioned action inadvertently turns her student into a scientific specimen.

Mr. C is a math teacher who notices when his students drift into daydreams. He actively checks in with his class and expresses empathy for those struggling to focus on cold, snowy days in the city.