Serendipity is a pink sea dragon who hatches from a large Antarctic egg discovered by Kōna (localized as "Bobby" in English), a shipwrecked boy who drifted to Pure Island. Her origins begin with this mysterious egg. Physically draconic, though sometimes called a dinosaur in adaptations, she wields unique abilities: flight, breathing both fire and ice, and using her tail defensively. Her distinctive pink coloration defines her appearance.

Playful and curious by nature, Serendipity exhibits a carefree spirit, easily distracted by new experiences which sometimes leads to unintended mischief. She possesses a strong protective instinct toward Pure Island and its inhabitants, demonstrating unwavering loyalty and courage when confronting threats, primarily the treasure-seeking pirate Captain Smudge. She actively collaborates with Kōna and others to defend their peace.

Her relationships are central. She shares a deep bond with Kōna, meeting him immediately after hatching, and their adventures form her core experiences. She forges significant connections with Princess Laura, the mermaid queen of Pure Island; the talking parakeet Pira-Pira; and other inhabitants like Prime Minister Dolf. These bonds emphasize friendship and collective problem-solving against external threats.

Serendipity develops from a naive hatchling into a proactive guardian of Pure Island, adapting to her protective role. She leverages her unique abilities and forms alliances to preserve the island's safety, integrating into the community with a growing sense of responsibility. Faced with the "But Now I Must Go" trope, she chooses to remain and protect her home. Serendipity's story unfolds solely within the original series and its compiled film adaptation.