When Master Yo accidentally breaks Yin's Two-ni-corn doll, she and Yang travel to the Valley of the Two-ni-corns to have it fixed. However, instead of happiness and peace, they find Ultimoose! Will they be able to restore peace to the valley?
At the mall Yin defeats many people in order to get a rare Two-ni-corn toy. While she is telling Yang all about her toy, Master Yo sits on the toy. To avoid paying for another toy he sends Yin and Yang to the Valley of the Two-ni-corns to ask their leader Rainbow Mane to fix her toy. When they get there they learn that Utimoose has taken over the Valley has cut off the Two-ni-corns horns and plans to melt the horns to make himself a bigger set of horns. In disguise as a big Two-ni-corn they get in to the factory, while Yang and the Two-ni-corns battle the guards Yin battles Ultimoose and he is easily beaten. Ultimoose then decides to put his new big horns and uses the magic only to discover that the Two-ni-corn magic cant be used for evil only good stuff. When he tries to use it to destory them again Rainbow Mane reflects it back at him turning him into a Two-ni-corn. Ultimoose uses his two-ni-corn magic to turn everything back to normal and as thank you Rainbow Mane fixes Yin's toy.
The episode ends with Master Yo sitting on her toy again and Yin screaming in anger.