Their interaction would be filled with tension. Pennywise is a more flamboyant in his fear - mongering, while the Babadook is more subdued and insidious. They might start by sizing each other up, trying to figure out the other's weaknesses. Pennywise might taunt the Babadook with his clownish antics, but the Babadook would likely respond with a menacing silence or a sudden, dark display of power.
One common theme is the allure of the unknown. Pennywise is such an otherworldly character, and in fanfiction, the reader is often drawn into his strange and mysterious world. Another theme is the battle between fear and attraction. The reader may be terrified of Pennywise but also strangely attracted to him.
Well, it might start during a strange encounter on a stormy night. The reader is out in the rain, and Pennywise appears. Instead of running away, the reader is drawn to Pennywise's otherworldly appearance. Pennywise, sensing this unusual connection, decides to approach the reader rather than terrify them, and from there, the love story could gradually unfold.
One big challenge would be the nature of Pennywise. He is a malevolent being who feeds on fear. The reader would constantly have to deal with his dark side. Also, society would not understand such a relationship. People would be horrified if they knew the reader was in love with a monster like Pennywise.
Some Tumblr blogs are dedicated to sharing and discussing fanfictions. You could search for relevant tags or ask in the fanfiction communities on Tumblr. There might be some users who can point you to great 'female Pennywise x male reader' fanfictions.
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.
There are quite a few. 'A Penny for Your Thoughts, Pennywise' is a story where the reader can almost read Pennywise's mind. It's a fascinating take on their relationship. 'Pennywise's Protective Side' is another one. Here, Pennywise shows his protective nature towards the reader, which is quite different from his usual menacing self in the movies. These fanfictions offer unique perspectives on the 'pennywise x reader' relationship.
One common theme is the unexpected encounter. Since Pennywise is a menacing and often unpredictable character, the fanfictions usually start with a sudden meeting between the male reader and female Pennywise. It could be in a spooky setting like the sewers or an abandoned house.
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.