In the fanfiction, it could be an old hermit who lives nearby. This hermit has a lot of knowledge about the local wildlife and their poisons. He could come across Elton Castee after the bite and use some herbal remedies that he has prepared over the years to treat the bite. Or perhaps a passing scientist who is studying black widows could use their specialized knowledge to help Elton Castee.
His friends could help him. They might drive him to the hospital or call for medical assistance. They could also stay by his side, trying to keep him calm and comfortable while waiting for help to arrive.
Well, it could start with Elton Castee being in his backyard. He's unaware that a black widow has made a home near his shed. As he reaches for something, the black widow bites him. This could set off a chain of events. He might first try to identify the spider to know how serious the bite is. Then, he could be faced with symptoms like nausea, sweating, and difficulty breathing. His journey from getting bitten to seeking proper medical attention or trying home remedies could be the main focus of the fanfiction.
It could be a rival spy agency. They might want to get information from her about S.H.I.E.L.D. and its operations. They would see her as a valuable source of intelligence.
She might be kidnapped by a supervillain who wants to use her skills for his own evil plans. For example, he could force her to break into a highly secure facility to steal some dangerous weapon or technology.
I'm not sure if there is an exact fanfiction where Spiderman gets Black Widow pregnant. Fanfiction writers can come up with very strange and unexpected storylines. However, from a canonical perspective, this doesn't fit with the established characters' storylines in the Marvel universe. Spiderman has his own set of relationships and story arcs, and so does Black Widow. So, while it might exist in the vast world of fan - created stories, it's not something that is likely to be widely known or accepted in the general context of the Marvel franchise.
His friends like Ron and Hermione would most likely be the ones to help him. They are always there for Harry in difficult situations.
One possible plot could be that Black Widow, while on a mission, gets hit by some sort of experimental weapon or magic spell that reverts her to a child. She then has to rely on her Avengers teammates to protect her while they search for a way to reverse the effect. Her skills as a child would be limited, but her intelligence might still be intact, leading to some interesting situations where she tries to communicate complex ideas in a child's body.
Maybe it was someone from her past in the Red Room. There could have been a forced relationship during her training days, and the consequences are now the baby. This would add a lot of drama and a darker tone to the fanfiction as she has to deal with this part of her traumatic past while raising the child.
Often, characters like Hawkeye might be paired with her. Their long - standing friendship in the original Marvel universe could translate into an interesting dynamic in the fanfiction. He could be someone who helps her adjust to her new form, or they could go on adventures together with her new - found size being an advantage.
A good antagonist could be a rogue S.H.I.E.L.D. agent who has his own plans for power. He might see Captasha and Black Widow as threats to his scheme. This agent could have access to some high - tech weapons and a group of loyal but misled followers.
Steve Rogers could be the one to help. Given their long - standing friendship, Steve would probably be there to offer some basic first aid or just some words of comfort.