Jam Ojisan created Anpanman when a shooting star crashed into his oven during anpan baking, bringing the hero to life and establishing Jam Ojisan as a foundational figure. He possesses extensive knowledge gained through youthful travels, reflected in the many books filling his bakery. His expertise spans bread-making and mechanical invention, producing devices like the Anpanman Mobile to aid others.

Physically resembling Anpanman but marked by age, he has gray hair, fluffy eyebrows, a mustache, and lighter red tints on his cheeks and nose. He consistently wears a white chef's hat, shirt, pants, apron, and blueish-gray shoes. Early printed material depicted him smoking a pipe, a trait omitted later.

Deeply kind and committed to helping others, Jam Ojisan acts as a paternal figure to Anpanman and other creations like Melonpanna and Currypanman. He encourages their growth, exemplified by urging Anpanman to always strive for his best. His compassion extends to antagonistic Rollpanna, whom he repeatedly invites to join the bakery community, hoping for her redemption.

Relationships are central to his character. He shares a deeply familial, non-biological bond with Batako, whom he may have known since infancy. His pet dog, Cheese, accompanies him but shares a lesser closeness than Batako. He maintains supportive connections with heroic allies like Shokupanman and aids fellow bread-based heroes such as Currypanman.

His technical skills frequently repair mechanical or robotic characters. He addresses critical needs, baking replacement heads for Anpanman when damaged and sharing parts of his own head to feed others. Within the series lore, both he and Batako are considered fairies, as humans do not exist. His role in narratives like "Soreike! Anpanman: Shabondama no Purun" consistently utilizes his baking and inventive capabilities to support the protagonists. His background and dedication to nurturing and protecting through culinary and mechanical means remain unwavering across the franchise.