Marvin the beetle is the main protagonist of Masterpiece, as shown through the limited third-person viewpoint that focuses on him. Marvin is a young beetle, the equivalent of a child in human terms. He lives with Mama and Papa and makes them very proud with his accomplishments. Marvin likes to swim and is the only one of his family that knows how, leading them to trust him with the retrieval of Mrs. Pompaday’s contact lens.

In a lot of ways, Marvin is unlike the other beetles in his family. While the others are very mistrusting of humans, Marvin sees that not all humans are dangerous, leading him to form a friendship with James. Despite his family’s warnings, Marvin is open to exploring new things, including leaving the apartment with James, which his parents are opposed to. Marvin exhibits the virtue fortitude throughout the novel, taking risks and making brave leaps to help James and save Fortitude from theft.

Marvin discovers his talent for drawing when he decides to give James a birthday gift with the pen and ink set. Marvin falls into a trancelike state when he makes art, forgetting about everything but his subject and the paper.