You can try searching on fanfiction websites like Archive of Our Own (AO3). They usually have a wide range of fanfictions, including South Park ones with a magical girl theme.
One common theme is the characters from South Park taking on magical girl personas. For instance, they might have to save South Park from some sort of evil in a magical way.
In South Park, there was a strange occurrence. A new kid moved into town, but this kid was a bit different. He was a super - smart alien in disguise. The boys, being the curious bunch they are, quickly noticed something was off. Cartman thought he could use the alien to take over the world, Kyle wanted to help the alien fit in, Stan was just confused, and Kenny was along for the ride. They all got into crazy adventures as they tried to figure out the alien's true motives and protect South Park from any potential threats.
Another theme is the adaptation to different environments. For example, the South Park kids might find themselves in the urban environment of New Girl's setting. How they cope with things like modern apartments, trendy cafes, and different social norms compared to their small mountain town is often explored.
In this fanfiction, Kyle could be dressing like a girl because he wants to understand the experiences of the female characters in South Park better. He starts to notice small things that girls go through, like different treatment in stores or on the street. This leads to him becoming an advocate for gender equality within the South Park community.
Maybe the story could revolve around Kyle, as a girl, trying to participate in activities that are usually dominated by boys in South Park. This could lead to some interesting conflicts and also show how gender roles are perceived in the town. He could also form new friendships or rivalries with the female characters.
In general, it's not highly popular. The concept of mpreg in South Park fanfiction is a very specific and somewhat strange concept that appeals only to a particular subset of the South Park fan base. Since it goes against the normal biological and story norms of the show, it doesn't gain as much traction as other fanfiction themes that stay closer to the original spirit of South Park.
First, you need to really understand the personalities of the South Park girl and the New Kid. Read up on their traits in the original show. For example, the New Kid is often quiet and observant, so keep that in mind when writing his actions and dialogue.
Some South Park New Girl fanfictions focus on the cultural differences between the two shows. The crass and often satirical nature of South Park contrasts with the more relationship - centered New Girl. Fanfiction writers might use this to create humorous or thought - provoking stories. For instance, they might write about how the characters from South Park would react to the loft living situation in New Girl.
It could be Cartman. Cartman is often the source of trouble in South Park. He might tease Kyle even more now that he's a girl, or try to take advantage of his new situation in some mean - spirited way.
One popular storyline could be the South Park girl helping the New Kid navigate the strange and crazy world of South Park. For example, she could introduce him to all the unique characters and their quirks.