In a 'Harry Potter facehugger' fanfiction, it could be that the facehugger is brought into the wizarding world by a Muggle - born student who accidentally carried it in a magical object from the Muggle world. The facehugger attacks a house - elf first. Dobby, for example, could be the victim. Then the wizarding community has to deal with this new threat. Hermione would start researching in the library to find any existing spells that could be used against it, while Ron would be freaking out and Harry would be trying to come up with a plan to save Dobby and prevent more attacks.
The professors at Hogwarts would have different reactions. Professor Snape might be secretly intrigued by this new and strange creature while outwardly showing disdain. Professor McGonagall would be concerned for the safety of the students and would start organizing protection spells around the school. Hagrid, being the lover of strange creatures, might try to approach it in a friendly way at first, until he realizes how dangerous it is.
The plot could involve a situation where a new form of dark magic is unleashed in the wizarding world, which spreads like wildfire and causes destruction similar to 911. The Ministry of Magic is caught off - guard. Hermione, with her vast knowledge, starts researching a way to counter this magic. Meanwhile, Ron and Harry lead the effort to protect the civilians. They set up shelters in places like the Room of Requirement and use Patronuses to guide people to safety. As they dig deeper, they discover that this dark magic was a planned attack by a long - hidden dark wizard group who wants to take over the wizarding world.
In a 'facehugger got me pregnant' fanfic, one possible plot could be a science - fiction horror - themed story. The character who gets 'pregnant' by the facehugger might be in a terrifying situation. They could be part of a group on an alien - infested planet or ship. The pregnancy might lead to all sorts of strange and dangerous developments, like the growth of an alien entity inside them that defies normal biological understanding. This could put their life at risk as well as the lives of those around them as they struggle to deal with this unnatural and horrifying state.
One possible plot could involve a group of spiders that have been enchanted by a dark wizard. These spiders start attacking Hogwarts students. Harry, along with his friends Hermione and Ron, would need to find the source of the enchantment and break it to save the school. They might have to explore the Forbidden Forest more deeply and face their fear of spiders to do so. This would combine the elements of adventure, mystery, and the existing spider lore from the Harry Potter series.
The plot could involve Catwoman being drawn into the wizarding world by some mysterious magical force. She might start out as an outsider, trying to figure out how things work. Maybe she gets involved in a plot to steal a powerful magical object, but along the way, she starts to have a change of heart and decides to help the good guys instead.
A plot could be that Gaster has a connection to the Forbidden Forest in Harry Potter. He might be the source of some of the strange and dangerous creatures there. As Harry and his friends explore the forest more, they start to notice Gaster's influence. Gaster could also be using the forest as a way to try and get back to his own world or to gain power in the Harry Potter universe. This would lead to a series of adventures and battles as the characters try to either stop Gaster or understand his motives.
In this fanfiction, the plot could center around Harry Potter arriving in Tamriel during a time of great unrest. He discovers that there are parallels between the magical hierarchies in Tamriel and Hogwarts. He could get involved in the political struggles of the various factions in Tamriel while also trying to find a way back home. Along the way, he might teach some of the Tamriel mages about some of the more advanced magic he learned at Hogwarts, like Patronus Charms, and in return, learn about Tamriel's unique magical artifacts and how to use them.
One possible plot could be that Harry discovers that the wizarding world was actually created by androids in the far future as a sort of historical experiment. So he has to use his magic skills to break free from the control of these androids who are now trying to manipulate the wizarding world for their own purposes.
Maybe Harry could be the host of the Kyuubi's power in the wizarding world. He would have to deal with not only the threats from Voldemort but also the power of the Kyuubi inside him. His friends might be both amazed and a bit scared of this new power source.
Well, it could be about Harry Potter somehow taking on the characteristics or abilities of Alastor Moody. Maybe he has to pretend to be Moody for a mission and in the process, he learns a lot about Moody's past and his way of dealing with dark wizards.