Jam Ojisan, known as Uncle Jam, created Anpanman and several other central characters. He appears as a kind, warm-hearted elderly figure possessing vast knowledge and expertise in bread baking. His resemblance to Anpanman includes age-related distinctions: gray hair, fluffy eyebrows, a mustache, and lighter red tints on his cheeks and nose. He typically wears a white chef's hat, shirt, pants, apron, and blueish-gray shoes.

Extensive travels in his youth contributed to his broad understanding of the world, reflected in the many books lining his room. Beyond baking, he is a skilled mechanic capable of constructing advanced mecha like the Anpanman Mobile and repairing robotic characters. He also rides motorcycles, demonstrating versatility.

He resides in a bread factory and is intrinsically linked to the "stars of life," celestial phenomena central to character creation. Anpanman came to life when a shooting star landed in Jam's oven during baking. This event established Jam as creator and father figure. He also crafted Melonpanna and Rollpanna. Early sources ambiguously attribute Currypanman's creation to him, though this reference remains inconsistent.

His personality centers on compassion and mentorship. He nurtures the heroes, encouraging their abilities and guiding their moral development, seen with Anpanman in infancy and Creampanda later. He maintains a soft spot for Rollpanna despite her antagonism, repeatedly inviting her to join the bakery. His relationships are familial: he regards Anpanman as his child, shares a deep non-biological bond with Batako (known potentially since her infancy), and cherishes Cheese the dog as a pet.

Jam and Batako are identified as fairies within the lore, as humans do not exist in the Anpanman World. Earliest depictions in the 1973 picture book and manga showed him smoking a pipe, discontinued later. His name was initially unspecified, referred to simply as "uncle" or "old man."