Perhaps there could be a story where Kenny and Cartman are forced to team up for a school project. They initially bicker and fight about how to do it, but as they dig deeper into the research or task at hand, they start to respect each other's ideas more. They could face external challenges like a bully trying to steal their project or a teacher who doesn't believe in their unorthodox approach.
One plot idea could be that Kenny and Cartman get involved in a time - traveling adventure. Maybe they accidentally go back in time and have to work together to get back to their own time, all while dealing with their usual differences and the challenges of the past era. Another idea is a body - swap situation where they have to experience life in each other's shoes, leading to a lot of comical and also some heart - warming moments as they understand each other better.