Jam-ojisan is Anpanman's creator and primary caregiver. His pivotal role began when a shooting star struck his oven during anpan preparation, miraculously bringing the bread-headed hero to life. This event established his enduring responsibility: he bakes replacement heads whenever Anpanman sacrifices part of his own to feed the hungry or sustains damage, with the damaged head detaching once a new one is applied. He embodies profound kindness and a nurturing disposition, prioritizing others' welfare and mirroring Anpanman's altruism. This extends to mentoring younger characters, offering fatherly guidance to Melonpanna and fostering Creampanda's abilities as an adoptive guardian. He persistently invites the unstable Rollpanna, affected by dual hearts, into the bakery community, maintaining unwavering affection for his creation.

Mechanical ingenuity defines a key aspect of his capabilities. He demonstrates this through inventions like the Anpanman Mobile and repairs performed on robotic characters. Extensive knowledge gathered during youthful travels fills his home library, aiding his problem-solving across diverse situations. Physically, he resembles Anpanman but exhibits age-distinct traits: gray hair, fluffy eyebrows, a mustache, and lighter red cheek and nose tints. His consistent attire features a white chef's hat, shirt, pants, and apron, paired with blueish-gray shoes. Additional skills include motorcycle operation and potentially undisclosed inventor-researcher talents.

Within Anpanman's universe devoid of humans, Jam-ojisan and Batako-san exist as fairies despite their human-like appearances. Their relationship reflects non-biological familial closeness through cohabitation and mutual care, possibly tracing back to her infancy. While early media implied he created Currypanman and Shokupanman, later narratives obscured these origins. He maintains supportive relationships with these bread heroes regardless of direct creation. His pet dog, Cheese, accompanies him, sharing a comparatively less intense bond than his connection with Batako-san. Early conceptual details like pipe smoking in the initial manga were omitted from later adaptations.