Today Tongwang Shi Sector is a Chinese computer animated TV show, centering around a boy named Tong Hua and his unexpected friend Xi Pu, that ran for 25 episodes starting from 2011.
Cake Eaters (S01E17)
Xi Pu is watching her weight, but Tong Hua tempts her into eating cupcakes. Eventually she gets a fat body and tries to exercise it off, but is so addicted to cupcakes that her face becomes fat. She gets revenge on Tong Hua by feeding him the cupcakes, fattening him up instantly.