Uncle Jam created Anpanman and other heroic characters in their world. He appears as an elderly figure with gray hair, fluffy eyebrows, a mustache, and light red-tinted cheeks and nose. Typically dressed in a white chef's hat, shirt, pants, and apron with blueish-gray shoes, he shares some features with Anpanman but is marked by age.

A kind and warm-hearted expert baker, he also possesses extensive mechanical engineering skills, enabling him to build and repair mecha machines like the Anpanman Mobile. His broad knowledge comes from youthful travels, reflected in the many books within his bakery. Though human-like, lore confirms he and Batako are "fairies" in a non-human populated setting.

Uncle Jam acts as a father figure and mentor, especially to Anpanman, whom he brought to life when a shooting star animated an anpan in his oven. He nurtures all his creations, encouraging them to help others and persevere, extending guidance to younger characters like Creampanda. His relationships are familial: a close non-romantic bond with assistant Batako, treating Cheese as a pet dog, and cautious concern for Rollpanna due to her unstable dual-hearted nature.

In the movie *Kagayake! Kurun to Inochi no Hoshi*, his bakery is central to Star Festival preparations. He maintains normalcy and support while Anpanman investigates mysterious black stars and the origins of Kulun, a child emerging from an egg in Baikinman's trash. The narrative ties to his foundational act of creation through the recurring "stars of life" motif.