Flopsie was KingBumi's pet goat gorilla. As such, he had a gorilla's face and body, a goat's hind legs, tail, eyes and horns, and a rabbit's ears and speed. Flopsie was extremely large, with big green eyes and enormous teeth. Despite his unnerving appearance, he was extremely affectionate and loved to have his belly scratched.
When Team Avatar first visited Omashu, Aang was assigned three challenges by King Bumi, the second of which involved Aang catching and retrieving Flopsie. Initially, Aang assumed that Flopsie was the small rabbit that Bumi had pointed out. After briefly fleeing for his life from a large goat gorilla that had charged after him, Aang realized his mistake, and called the goat gorilla Flopsie, passing the test.
Aang encountered Flopsie a second time when he returned to Omashu looking for Bumi, freeing the large creature from being used as forced labor by the Fire Nationsoldiers. Aang attempted to ride the animal, and, out of habit, commanded him using "yip yip", a phrase he used to command Appa to fly. After the beast remained still, Aang realized his mistake, and instead used the command, "Let's go!". This time, Flopsie took off running. After Aang searched the entire city of Omashu in vain for a trace of King Bumi, Flopsie escorted him to the Omashu Resistance camp.