Uncle Jam crafts Anpanman and serves as his primary caregiver. This kind, warm-hearted fairy, not human, possesses extensive knowledge of bread baking. His appearance echoes Anpanman but features gray hair, fluffy eyebrows, a mustache, and lighter-tinted cheeks and nose. He typically wears a white chef's hat, shirt, pants, apron, and blueish-gray shoes.

Significant mechanical skills allow him to construct functional mecha like the Anpanman Mobile and repair robotic characters, alongside riding motorcycles. His creations include Anpanman, born when a "star of life" landed in his oven. He also baked Melonpanna and Rollpanna, though Baikinman's interference caused Rollpanna to develop an "evil blue heart." Early materials suggested he created Currypanman, later retconned as uncertain.

He maintains close familial bonds. Acting as a father figure, he encouraged Anpanman from infancy toward heroism and similarly supports Melonpanna and Creampanda. Despite Rollpanna's instability, he persistently invites her to join the bakery, reflecting a soft spot. He lives with Batako, sharing a deeply familial bond and responsibilities in raising Anpanman and maintaining the bakery.

Functionally, he sustains Anpanman's heroism by baking replacement heads when the original is damaged or depleted, restoring his strength and abilities, and provides new heads for other bread-based heroes as needed. Influenced by creator Takashi Yanase's wartime starvation, Uncle Jam embodies themes of sustenance and resilience as a symbol of nourishment and hope.