Jam Ojisan is the creator of Anpanman and other bread-based heroes. Legend has it that a shooting star landed in his oven while he baked an anpan, miraculously bringing the bread to life and establishing his foundational role in the series.

He physically resembles Anpanman but displays elderly traits: gray hair, fluffy eyebrows, a mustache, and lighter red cheeks and nose. He consistently wears a white chef's hat, shirt, pants, apron, and bluish-gray shoes.

He embodies profound kindness and a commitment to helping others. His extensive travels in youth gave him vast knowledge, evident in the many books filling his home. He possesses expertise in both baking and mechanics, enabling him to build advanced machines like the Anpanman Mobile and repair mechanical characters.

Relationships are central to him. He shares a deep fatherly bond with Anpanman, having raised him from infancy and inspired him to fight for justice. He extends this caretaker role: he created Currypanman according to early media (though later sources present this origin ambiguously), acts as a father figure to Melonpanna, and mentors Creampanda much like he did young Anpanman. He shows persistent concern for the antagonistic Rollpanna, repeatedly inviting her to join the bakery. Though unrelated by blood, he shares a close familial bond with Batako, collaborating on bakery operations and maintaining the heroes' capes. His pet dog Cheese accompanies him, though their bond appears less profound than his connection to Batako.

He belongs to a distinct category within the story's universe; both he and Batako are considered fairies, as humans do not exist in Anpanman World. Early artistic depictions showed him smoking a pipe, but this detail was removed early in the series. His name sometimes appears as "Mr. Jam" in English, and initial picture books referred to him simply as "uncle" or "old man" before his current name was established.