Once a bustling attraction, the Ba Sing Se Zoo had become worse and worse over the years. After the budget for the zoo was cut, there was no money for its upkeep. All the zoo employees except for Kenji, the zookeeper, had left, and the zoo became a dilapidated place.
In 100 ASC, when Team Avatar arrived in Ba Sing Se, Aang, while flying high over the city in search of Appa, landed at a small farm. Around the zoo, he saw a wide variety of animals, all of which were miserable in their small cages and partially starved. Kenji told Aang that the zoo was no longer receiving funding from the Dai Li because the children had stopped coming. Nobody came to the zoo because it was also quite filthy and one of the cages showed an animal lying near multiple piles of feces. When Kenji said that he would have liked nothing more than to let his animals run wild in open spaces, Aang suggested moving the animals to an open area just outside the city, near the Agrarian Zone.
The animals proved much more difficult to control than Aang had originally thought and they ended up running wild all over the city, terrorizing the citizens. Hog monkeys destroyed a shop, various animals attacked the citizens, and the cabbage merchant had his cabbages eaten by a rabaroo. After unsuccessfully trying to restore order, Aang pulled out his bison whistle and blew a huge burst of air through it using airbending, which drew the attention of the animals. He then hopped on an air scooter as the animals ran after him.
Meanwhile, Kenji frantically tried to get the guards to open the gate, who refused until they saw the oncoming stampede. Once the gates were opened, Aang flew past the stampede on his glider, and then created another air scooter to ride. Using earthbending, he created a wall around the animals and continued to earthbend paths, secluded areas, and habitat features. The children and their families came flocking to the new zoo and the zookeeper thanked the Avatar for his help, and he told Aang he should have a job with animals. However, the zoo animals were not the only creatures that followed the sound of the whistle, as many cats, dogs, and cat-dog hybrids were also inside the animal pens, causing the zookeeper to change his mind and said that Aang should "stick to helping people".