Fat was a swordsman who served as Piandao's loyal yet disgruntled butler. A serious man, Fat did not find many things humorous. He prepared meals and beverages for Piandao and his students, whom he also assisted in training.
Fat came to Piandao many years before Sokka's visit and proved his worth by cooking him a delicious dinner. Piandao trained Fat in exchange for some good, home-cooked grub, and the two have been together at Piandao's castle ever since.
Upon Sokka's arrival at Piandao's door step, Fat warned him that Piandao was notorious for turning nearly every aspiring student down. After Sokka subsequently failed to procure a token that would prove his worth, Fat was skeptical that the young Water Tribe warrior would be allowed to train at the estate, though granted him access to the castle nonetheless in order to face Piandao. He was present when Piandao agreed to train Sokka and subsequently became the young man's training partner, easily overpowering and humiliating him in their earlier battles. When Sokka's training led him to rearrange the courtyard of the castle, Fat became upset at the considerable mess Sokka made. As Sokka's training neared its end, Fat was bested by Sokka in a one-on-one swordfighting match. Although he was less than pleased with being beaten by the young man, Fat held no grudge and aided Sokka in the procurement of pieces of meteor to forge the latter's sword with.
When Sokka and his friends were leaving, Fat stopped them just outside the castle gate, saying that Piandao had sent him a gift to remember him by. He handed Sokka a small sack, inside of which was a white lotusPai Sho tile, and bowed respectfully before returning inside.