The interactions between Sans and the characters from the other crossover element are very important. For example, if it's a crossover with a fantasy world, how does Sans interact with the magic - using characters? Does he use his own unique skills to complement or contrast with them? Another aspect is the world - building. How well does the author create the new combined world? Is it believable and immersive?
One popular sans the skeleton crossover fanfiction is 'Underfell x Undertale: Sans Swap'. It offers an interesting take on character swaps between the two universes. The story plays with the personalities and relationships in a unique way.
In terms of the plot of such a fanfiction, it could involve them teaming up against a common enemy. Maybe they have to face some sort of interdimensional threat. Their different abilities, Dave's with his time - related powers and Sans' bone attacks and teleportation, would make for an exciting combination in battle.
The theme of adaptation also fits. They are in an unfamiliar situation, meeting a character from a completely different world. So, they have to adapt to each other's presence, ways of thinking, and powers. This process of adaptation can drive the story forward and also show how characters can grow and change in new and unexpected situations.
Papyrus also shows up often. His relationship with Sans adds an interesting dynamic to the crossovers. And his own unique personality and abilities can lead to various plot developments when combined with other crossover elements.
The theme of chaos and order also appears frequently. When Sans crosses over into other universes, it can disrupt the existing order or he might be the one to bring order to a chaotic situation. This creates interesting storylines as he has to navigate through these new power dynamics and relationships. Also, there can be a theme of redemption in some cases, where Sans helps a character who has made mistakes in their own universe.
One interesting sans crossover fanfiction could be where Sans from Undertale crosses over with the world of Harry Potter. He might use his unique abilities like teleporting to surprise the wizards in Hogwarts. Another could be a crossover with the Pokémon world, where Sans teams up with Pikachu. Maybe he'd use his bone attacks along with Pikachu's electric shocks to battle villains.
One interesting concept could be the clash of different universes' rules. For example, when Sans from the Undertale universe meets characters from other crossovers, the way their powers interact. Sans' unique abilities like teleporting and bone attacks might be affected by the new environment or powers of the crossover characters.
One popular storyline could be Error Sans crossing over into the Undertale main timeline and causing chaos among the characters. He might try to disrupt the peace that the main characters have worked hard to achieve. Another could be a crossover with a different AU (Alternate Universe), like Error Sans meeting characters from Underfell. In this case, the clash of their different personalities and the rules of their respective universes can create interesting conflicts and interactions.
The exploration of different universes. Crossover fanfiction allows readers to peek into different fictional universes through the eyes of Reaper Sans. It's like taking a journey into uncharted territories. We get to see how the rules, cultures, and beings in these other universes compare and contrast with what we know from the original Reaper Sans setting. This exploration aspect can be really exciting as it broadens our imagination and gives us new perspectives on familiar characters.