While staying in Ba Sing Se, Aang found a gloomy and desolated zoo, where all the animals were kept in small cages; one of the present beasts was an elephant mandrill, who laid hopelessly in a pen that was too small for his size. Deciding to help the animals, Aang released all creatures in order to guide them through a larger facility right outside the city's walls. However, while being free, the elephant mandrill rampaged through the streets of Ba Sing Se, scaring its civilians. The animal could not be controlled, until it heard the signal of Aang's bison whistle, and followed the sound outside the city's wall, where elephant mandrill ended up in a larger and greener pen in the newly created zoo.
The elephant mandrill is a hybridized creature with the body of an elephant, and the colorful head of a mandrill, a baboon-like primate. Its stocky body, with the exception of its elephant-like legs, is covered with shaggy brown fur.
The elephant mandrill has the shaggy fur coat and distinctive face of a mandrill. The male mandrill has the most vividly colored face of any mammal, with a scarlet band of hairless skin that extends down from between its eyes, flaring out to cover its nostrils, and flanked by vertical bands of blue skin on either side. Its lower jaw is adorned with an orange-yellow beard. The elephant mandrill's connection to the elephant is its massive size and its legs.