Jam-ojisan is Anpanman's creator, born when a shooting star streaked into his oven as he baked an anpan pastry. His shelves overflow with books reflecting the vast knowledge gained during extensive youthful travels. He resembles Anpanman but with aging features: 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, and apron, paired with blueish-gray shoes.

Warm and caring, Jam-ojisan dedicates himself to helping others and spreading happiness. His expertise extends beyond baking bread to proficiently cooking various dishes and constructing advanced mecha machines like the Anpanman Mobile. He repairs robotic or machine-based characters, incorporating functionalities like super hearing for Anpanman to detect global distress calls. He also rides motorcycles.

Jam-ojisan shares a deeply parental bond with Anpanman, having raised and encouraged him since infancy. His relationship with Batako is explicitly non-familial but akin to close-knit family through shared residence and mutual care, potentially dating back to her infancy. He acts as a father figure to Melonpanna, supports Creampanda's abilities as an adoptive child, and maintains a soft spot for Rollpanna despite her antagonistic tendencies, repeatedly inviting her to join the bakery inhabitants. His pet dog, Cheese, remains a companion, though less central than Batako.

Within the Anpanman universe, Jam-ojisan and Batako are categorized as fairies, as humans do not exist despite their human-like appearances. In *Soreike! Anpanman: Kuroyukihime to Motemote Baikinman*, he appears as a supporting character during events involving Baikinman's abduction by Princess Kuroyukihime and the ensuing chaos of turning things black. His role in other media, such as the movie *Sore Ike! Anpanman: Kieta Jam Ojisan*, involves narrative focus on his disappearance.