In fanfics, characters might want kids for the purpose of redemption. Maybe a character who has made mistakes in the past sees having a child as a way to start anew and be a better person. They could teach the child right from wrong and in doing so, find their own path to redemption. Also, the characters may want to build a community. By having kids, they can contribute to the growth of the demigod community at Camp Half - Blood or other places, ensuring its survival and prosperity.
One reason could be to carry on their heroic lineage. In the Percy Jackson universe, the demigods have such unique powers and abilities. Having a child would mean passing on those gifts. For instance, if Percy had a son, he might inherit Poseidon's powers over water. Another reason is the sense of family. Many of the characters have lost family members or have had a difficult family life. Having kids could give them a chance to create a loving, stable family unit of their own.
In Percy Jackson fanfics, different characters might have different views on having kids. For Percy himself, he might be hesitant at first. He's been through so much adventure and danger, and he might worry about bringing a child into a world full of monsters. But on the other hand, he has a strong sense of family and love, so he could also see the appeal of having a family of his own. Annabeth, being the strategic thinker, would probably consider all the implications carefully, like how to protect the child and educate it in the ways of the demigod world.
One reason could be for shock value. Writers might want to create a completely different and unexpected version of Percy to draw readers in. Another reason could be to explore a different type of relationship dynamic that isn't present in the original books. Maybe they want to see how Percy would act in a more romantic or flirtatious role, rather than his usual heroic one.
Perhaps he has been exposed to some sort of deadly and unknown substance in the mythical world. This could be a new type of monster venom or a strange plant that he accidentally ingested. The substance could be attacking his body from the inside, causing his internal organs to bleed, and thus he throws up blood.
He might meet other inter - galactic beings. For example, some sort of space - faring demigods from a far - off galaxy. Or he could encounter powerful entities that are the rulers of other planets.
First, in the original Percy Jackson story, Sally is a loving mother. Changing this fundamental aspect of their relationship goes against the established character traits. Second, it's an extremely disturbing and inappropriate concept, especially considering the target audience of the Percy Jackson series which includes young readers. Third, it violates the positive and family - friendly atmosphere that the series has created.
It could be due to some sort of poison or magical spell. In the Percy Jackson universe, there are all kinds of creatures and magic that could cause such a reaction. For example, if he was exposed to a slow - acting venom from a mythical beast, it might gradually make him faint.
One possibility is that the collar is a key to a hidden realm. Percy discovers this when he picks it up. He then has to journey to this realm, which is full of strange and dangerous creatures that are somehow related to Artemis. Along the way, he makes new friends and enemies as he tries to figure out how to use the collar to get back home.
As a punishment. He could have angered a powerful being, like a minor god or an elder at Camp Half - Blood, who decides that wearing a dress is a fitting form of humiliation for his misdeeds.
One reason could be that they love the original Percy Jackson books so much that they want more of the story. Fanfiction gives them that extra content. Another reason might be that they are interested in seeing different interpretations of the characters. For example, how a character might react in a different situation.
Another reason might be that she is forced to leave. There could be a magical or divine force at play. Maybe a god or goddess, who has some grudge against Percy or his father Poseidon, manipulates the situation so that Sally has no choice but to abandon Percy. This would add a lot of drama and conflict to the fanfic.