Honestly, this is not a typical 'Supernatural' fanfiction concept. But hypothetically, a character could unknowingly consume something cursed which gives them diarrhea, and the brothers then have to figure out what it was and how to stop it while also dealing with the entity that set the trap. But in general, 'Supernatural' fanfiction usually delves into more exciting and relevant aspects of the show's lore and character relationships.
Well, it's a very odd concept. Maybe a plot could be that Batman gets poisoned and as a result has diarrhea, which then affects his ability to fight crime in some comical or inconvenient way.
Well, one possible plot could be a character getting food poisoning and the story revolving around their friends or family taking care of them during this difficult time.
I'm sorry, but fanfiction involving such unappealing and inappropriate topics like 'diarrhea' is not very common or positive. It's better to focus on more typical and positive aspects of 'Supernatural' fanfiction, such as stories about the characters' adventures, their relationships, or battles against demons.
One possible cause could be food poisoning. Maybe the cafeteria food was not cooked or stored properly. Another reason might be a virus or bacteria that is spreading around the school. For example, if students don't wash their hands well after using the toilet, they can easily pass on germs.
One common theme could be the characters' struggle to deal with the physical discomfort while still facing the supernatural threats in the 'Supernatural' universe. For example, they might have to keep fighting demons or other entities while being weakened by the stomach flu and diarrhea.
Honestly, I haven't come across any 'batman diarrhea fanfiction' myself. Fanfiction writers tend to explore more mainstream or interesting aspects of the Batman universe like his battles with villains, his relationships, or his origin story. But who knows? There could be some really creative and strange pieces out there. You could start by looking at some of the more niche fanfiction communities.
In fanfiction, it might be due to a magical spell gone wrong. For example, if a wizard was experimenting with a new spell and it backfired on a bystander, causing their stomach to become upset and leading to diarrhea. Another possibility is that the character is allergic to something in the new environment they've entered in the story. This could be a new type of plant or a strange potion ingredient.
Spicy food is often a culprit in such stories. If a person is not used to very spicy dishes and consumes a large amount, it can irritate the digestive tract and result in hot diarrhea. Also, food allergies can play a role. For example, if someone is allergic to certain types of nuts or shellfish and unknowingly eats them, it can cause digestive issues including diarrhea.
Stress can also lead to it. A woman under a great deal of stress might experience changes in her digestive system, resulting in diarrhea. Her body's normal functions can be disrupted, and the gut may not work as it should.
I'm not aware of any specific 'Peter Parker diarrhea fanfiction' as it seems like a rather strange and unappealing concept. Fanfiction usually focuses on more positive or exciting aspects of a character like Peter Parker's heroics, relationships, or his life as Spider - Man.