Custard resides at St. Morwald's Home for Children and is Earwig's primary companion during their time there. He has short blond hair styled in a distinctive bowl cut. His demeanor is marked by profound timidity, often showing reluctance or fear during Earwig's activities, like their unauthorized climb into the church bell tower where she deliberately teased him with frightening scenarios. Despite his cautious nature and Earwig's tendency to challenge or mock it, he demonstrates consistent loyalty to her, maintaining their friendship.

He expresses a sincere desire for adoption and family life, a direct contrast to Earwig's contentment at the orphanage. He voices this longing atop the bell tower, questioning if she ever thought about life beyond St. Morwald's. Following Earwig's adoption by Bella Yaga and Mandrake, Custard displays evident apprehension towards her new guardians, particularly the imposing Mandrake. This fear persists even after Earwig gains control; she notes his refusal to visit due to terror of Mandrake during Christmas. Ultimately, Custard arrives at the house alongside Earwig's mother, though his interactions within this new dynamic remain unexplored.

His nickname originates from wordplay; Earwig adapted his birth name, John Custer, into "Custard," reflecting her influence. His role remains tied to his experiences alongside Earwig at the orphanage and his cautious approach towards her transformed life afterward.