The OC could be a psychic who is unknowingly drawn to Derry because of Pennywise's presence. Their psychic powers allow them to sense Pennywise's energy but not fully understand what it is at first. As Pennywise tries to manipulate the OC, the OC starts to fight back using their psychic abilities, creating a battle of wills and powers that could span across different dimensions within Derry, from the sewers to the abandoned houses and the mindscapes of both characters.
A really interesting plot could be that the reader is a paranormal investigator who has come to Derry to study the strange disappearances. They end up encountering Pennywise, but instead of being a victim, the reader uses their knowledge of the supernatural to communicate with Pennywise. The two form an unlikely alliance to uncover a deeper mystery in Derry that is related to Pennywise's origin, and during this process, their relationship evolves in unexpected ways.
Another idea is that Pennywise's pregnancy is the result of some sort of dark magic or a pact with an even more sinister force. The fanfiction could explore how Pennywise navigates this new situation, whether it tries to hide it from its usual prey or uses it as a weapon. For example, it could pretend to be a vulnerable pregnant entity to lure in those with a sympathetic nature, only to reveal its true self at the last moment.
One plot idea could be that Pennywise and the Babadook team up to haunt a small town in a unique way. They combine their powers of fear - Pennywise with his shape - shifting and the Babadook with his dark, shadowy presence. Another could be a battle between them for the most feared entity title, which causes chaos in the spiritual realm they inhabit. And perhaps they both target the same person who has a special ability to see and interact with them, leading to a strange alliance between the victim and one of them against the other.
Well, a possible plot is that Fem Pennywise has some sort of connection to the tailed beasts in Naruto's world. Naruto discovers this and tries to figure out how to use it to his advantage or to stop her if she has malicious intent. Or perhaps Fem Pennywise uses her shape - shifting abilities to infiltrate the Hidden Leaf Village, and Naruto has to expose her before she causes chaos. They could also form an unlikely friendship where Naruto teaches her about friendship and loyalty, which are concepts she's never really understood before.
One idea could be that the OC is a healer who stumbles upon Frankenstein's monster in the woods. The OC decides to help the monster, despite the danger, and they form an unlikely bond. This could lead to a story of redemption for the monster and a journey of self - discovery for the OC.
Maybe the OC is a scientist who has developed a device that can temporarily steal The Flash's speed. At first, the OC uses it for personal gain, but then realizes the chaos it's causing in the city. They then team up with The Flash to take down other villains who are after the device. Or, the OC could be a meta - human with the ability to see the future in flashes. The Flash initially doesn't trust the OC, but as they start to have the same visions, they have to work together to prevent a major disaster from happening.
The OC could be a researcher studying digimon behavior. Renamon becomes the subject of the study. At first, Renamon is very guarded around the OC. However, as the OC shows genuine respect for Renamon and her kind, Renamon begins to open up. They then embark on a journey to discover more about the history of digimon, with their relationship growing stronger along the way.
Well, an interesting plot could involve an OC that is a transfer student, just like the protagonist. But this OC has a hidden past related to the Metaverse. Maybe they were experimented on by a shadowy organization in their home country, and this gives them a different perspective on the Metaverse compared to the Phantom Thieves. Their goal could be to find out who was behind those experiments and get revenge. Along the way, they form a bond with the group and learn new ways of using their powers.
One idea could be that the OC is a new Keyblade wielder who meets Ventus during his training. They start as rivals, constantly competing in battles and challenges. But as they face a powerful enemy together, they realize their combined strength and start to develop feelings for each other.
Maybe the OC is a time - traveler who accidentally lands in Obito's time. She knows about his future actions but instead of trying to stop him right away, she tries to understand his pain. This leads to a complex relationship where Obito is both intrigued and afraid of her knowledge.