* Lily: The protagonist, a curious and observant young girl. She's the one who discovers the mysterious coin and becomes central to unraveling the mystery.
* Sam (or sometimes another name): Lily's friend or sibling, often a boy, who helps her in the investigation. Their role is often supportive but important.
* Various adults: These characters might be parents, teachers, librarians, or shopkeepers who may unintentionally provide clues or offer help to Lily and her friend as they try to solve the mystery of the disappearing coin.
It's important to note that the supporting characters are often less defined and more interchangeable than Lily and her immediate companion. The focus is primarily on Lily's investigation and problem-solving skills.