One great idea for a fanfiction could be a story where Underswap Sans and Underswap Papyrus go on an adventure in the Underground. Maybe they encounter a strange new monster that no one has ever seen before. They have to use their unique abilities to figure out how to deal with this new threat.
Common themes include loyalty. They are extremely loyal to each other in most fanfics. Another one is the theme of overcoming challenges. Whether it's dealing with other characters or facing difficulties in their world, they work together to overcome them. There's also the theme of fun and humor. Their interactions are often filled with jokes and light - hearted moments, which makes the fanfics enjoyable to read.
Underswap Papyrus is an interesting character. In fanfiction with a reader, it often explores a unique relationship. The fanfictions might show his charming, kind and sometimes goofy side. It could be about an adventure where he and the reader go through challenges together, or just a slice - of - life story where they get to know each other better.
A plotline could be that they discover a hidden part of the Underground. This new area could have different rules and strange creatures. They have to adapt quickly to survive and also figure out how this new place relates to the rest of the Underground.
Well, there's a fanfic called 'Underswap Bond'. In this one, it really focuses on the deep emotional bond between Papyrus and Sans. It has some really cute moments where they rely on each other and understand each other better than anyone else in their world. There's also 'Swapped Skeleton Adventures' which is more of an action - filled fanfic that still manages to show their great relationship.
There's also 'Swap Brothers' Bond'. This fanfic delves deep into the brotherly bond between Sans and Papyrus in the Underswap setting. It shows their daily adventures and how they support each other. The author does a great job of capturing the essence of their swapped selves, and it's full of humorous and touching scenes.
One popular trope is the 'fish out of water' scenario. The reader, often being from a different world or just not used to the Underswap universe, has to adapt, and Papyrus helps them. Another is the 'unlikely friendship/romance' trope, as Papyrus' exuberant personality might seem at odds with the reader at first.
A great Underswap Sans x Papyrus fanfiction might be the one that delves into their backstory. It could explore how their relationship developed from when they were younger. Maybe there was a time when they had a big fight but then learned to understand each other better. This kind of story can be really heartwarming as it shows their growth and the strength of their brotherly love.
A third common theme is self - discovery. Both Papyrus and Sans might learn new things about themselves as they interact with each other and face various situations. This can be really interesting as it shows their growth as characters. For instance, Papyrus might discover a new side of his personality when he has to protect Sans in a dangerous situation.