Well, in a 'sans meets bill cipher fanfiction', there could be some really interesting interactions. Sans, from Undertale, is known for his laid - back yet mysterious nature, while Bill Cipher from Gravity Falls is this chaotic and powerful entity. The fanfiction might explore how Sans would react to Bill's mind - games and manipulations. Maybe Sans would use his unique abilities like teleporting and bone attacks to counter Bill's tricks. It could also be a story of an unlikely alliance between the two, or perhaps a battle of wits and powers that keeps readers on the edge of their seats.
Well, it could be about Gaster suddenly reappearing in the lives of Sans and Papyrus. Maybe he has some important knowledge or a mission for them. For example, he might need their help to fix something in the Underground that's going wrong.
Obviously, Sans and Papyrus are the two main characters who we already know well from the original Undertale. They have distinct personalities that will play a big role in how they interact with Gaster. Gaster, on the other hand, is the enigma. His presence will likely drive the story as Sans and Papyrus try to figure out who he is now and what he wants, so he's also a main character in this fanfiction.
It's the personalities of the characters. Sans is a fan - favorite with his cool - headedness and dry humor. Bill Cipher is this all - powerful and unpredictable being. Putting them together in a fanfiction means there will be unexpected twists and turns as their personalities clash or, surprisingly, find common ground.
I'm not entirely sure specifically what that fanfiction is about. It could potentially be about Bill Cipher achieving or obtaining Will Cipher in some way, perhaps in a strange or otherworldly scenario within the context of the Gravity Falls universe. It might involve some sort of power play or a very unique plot device that only fans who have read it would know for sure.
I think Kakashi would also be a great character to pair with Bill Cipher. Kakashi is very intelligent and experienced. His encounter with Bill Cipher would be full of mind - games as he tries to figure out Bill's motives and powers while also protecting the village from Bill's chaos.
The main difference is the form. In the original, Bill Cipher is his non - human, otherworldly self. But in fanfic, as a human, his physical limitations and advantages are different. He might not have the same instant, all - powerful abilities.
Dipper Pines could be one of the main characters. He might be the one who first discovers Bill's transformation and tries to figure out if it's a trick or if Bill is truly changing. His inquisitive nature would make him a great foil to Bill's new human self.
One idea could be Bill Cipher getting trapped in a human form and having to navigate the strange world of human emotions and social norms. It would be a comical yet thought - provoking plot as he tries to understand things like friendship and love while still having his devious nature.
Papyrus might be initially shocked. He's used to Sans being more laid - back, so seeing him in a fight could be quite a surprise. His eyes would widen and he might gasp.