In Ponyo, the goldfish who turns into a human is Ponyo. She begins life as Brunhilde, the daughter of the underwater wizard Fujimoto and the sea goddess Gran Mamare.
Ponyo escapes from her father during an outing and becomes trapped in a glass jar near a seaside town. A five-year-old boy named Sōsuke rescues her, cuts his finger on the jar, and names her Ponyo. After tasting his blood, she develops a powerful desire to become human.
Her transformation is not merely a disguise. Ponyo’s magic disrupts the balance of nature and contributes to a devastating tsunami. Gran Mamare explains that Ponyo may remain human only if Sōsuke can love her regardless of whether she is a fish or a person.
The other options are important characters but not the goldfish: Fujimoto is Ponyo’s father, Gran Mamare is her mother, and Sōsuke is the human boy who befriends her. The title character’s name is therefore the film’s central answer.