One time my horse took over a city.
Two equestrians are selected to participate in a trial of a revolutionary new grain mixture for their sport horses, designed to significantly improve their existing athletic performance. Little do they know that their mounts will collect too much power, and get so strong and smart from the grain that they become power hungry and overtake their barn, and eventually, the town. This leads the humans into a more primitive state and the owners must take desperate measures to stop the chaos.
Special thanks to Kelsea being a trooper.