Yes, there are likely some out there. Some might explore different relationships he could have with female characters in unique storylines. Maybe they could be about a female character befriending Eric and changing his ways in some comical or heartwarming ways.
Often, there are themes related to how her personality might be different or the same as the male Eric Cartman. Some fanfiction might focus on her having a different role within the group of friends. For instance, she could be more empathetic or more of a leader in certain stories. And in some cases, the fanfiction may explore how she deals with the unique South Park culture from a female perspective, which can include everything from school to the town's strange events.
Well, obviously Eric Cartman is a main character. Then there would be his friends like Stan, Kyle, and Kenny. But it could also involve other South Park residents like Mr. Garrison, Chef (if in the right continuity), and even the parents of the kids. Since it's 'x everyone', it can really include just about any character from the South Park universe.
There are some fanfiction works that might explore the idea of a female Eric Cartman. Some could be about how her character would interact differently in the South Park universe with her friends. Maybe she'd have different relationships or face different challenges. You could also check out some South Park fan forums where fans might discuss or even share their own female Eric Cartman fanfiction ideas or links to such stories.
You could try fanfic websites like Archive of Our Own. It has a large collection of fan - created works, and there might be some female Eric Cartman fanfics among them.
There's a fanfic called 'Cartman and Kyle: A New Understanding'. It starts with their typical rivalry but then delves into how they start to see each other in a different light. It's quite engaging as it shows their relationship evolving in a very unexpected way. It also has some really funny moments that are true to the South Park style.
Another theme is the exploration of their personalities. How Cartman's often self - centered and mean - spirited nature can be changed or at least influenced by Kyle's more moral and kind - hearted character. And vice versa, how Kyle deals with Cartman's antics on a more personal level.
Another theme might be the development of an unlikely relationship. Given their contrasting natures, it could be about how they gradually come to understand and care for each other in the fanfic world. It could involve a lot of character growth for both of them. For example, Cartman might learn to be less of a bully and Wendy might learn to be more patient with him. And this relationship development could be set against different backdrops like school events or adventures in South Park.
In some 'eric cartman x everyone fanfiction', there might be a story where Cartman starts a big project that involves the whole community. For example, he could be trying to build the world's largest amusement park in South Park, and he has to convince everyone to help him. This would lead to all sorts of comical and chaotic situations as he tries to manage different personalities.
Well, I'm not sure about specific 'eric cartman x wendy fanfic' stories. But you could try looking on some popular fanfiction websites like FanFiction.net or Archive of Our Own. Just search for their names there and you might find some interesting reads.