Well, it could be really interesting. Deltarune might find the different interpretations in the fanfiction quite fascinating. It could see new takes on the characters it might be related to from Undertale. Maybe it would be inspired by the creativity of the fanfic writers.
One common theme is the exploration of the differences and similarities between the two worlds. Since Undertale and Deltarune have different settings and rules, fanfictions often play with how the characters react to these differences. Another theme is friendship. Characters from both games often form new friendships or strengthen existing ones across the world boundaries.
One interesting concept could be the crossover of characters' personalities. For example, how the determination trait from Undertale might interact with the more mysterious elements in Deltarune. Another could be the exploration of different timelines. Since both games have some elements related to time and alternate realities, a fanfic might delve into how these timelines could cross or affect each other. Also, the unique magic systems of both could be combined in creative ways, like how the soul powers in Undertale might work with the magic in Deltarune.
One idea could be that the characters from Undertale find themselves in the world of Deltarune. For example, Frisk could end up in the Dark World and have to figure out how to get back home while interacting with the Deltarune characters. They might team up with Kris to fight against new threats that are a combination of both universes' villains.
Maybe in the fanfiction, the Dark Fountains from Deltarune start appearing in the Undertale world. This causes chaos as the monsters in Undertale don't understand what these strange fountains are. Frisk, along with the Deltarune trio, has to figure out how to stop the fountains from spreading darkness. They could learn from each other's powers and strategies. For example, Frisk could teach Kris about determination in a more in - depth way, and Kris could show Frisk how to navigate the strange new areas created by the Dark Fountains.
Another plot idea is a story where the antagonists from both games, such as Flowey from Undertale and the King from Deltarune, form an alliance. Their goal could be to take over both universes. This would force the heroes of both games to work together. The fanfic could explore how the different characters with their own powers and personalities interact and strategize to defeat this powerful alliance.
Well, in undertale x deltarune fanfic, to explore friendship, it could start with characters being curious about each other. Let's say Papyrus from Undertale meets Susie from Deltarune. Papyrus's enthusiasm and Susie's tough exterior could lead to an interesting dynamic. As they get to know each other, they find common ground, like their love for adventure or their desire to protect their friends. This could then develop into a deep friendship where they would go to great lengths to help one another, even in the face of danger. And as more characters get involved, a whole network of friendships could be formed, showing that no matter where you're from, friendship can thrive.
Well, 'The Bridge Between Worlds' is a really good 'undertale x deltarune fanfiction'. It delves into the idea of building a bridge, not just literally but also metaphorically, between the two worlds. The characters from both sides start to understand each other's cultures and powers. There are some really cool fight scenes where the unique abilities from both Undertale and Deltarune are combined in creative ways.
Definitely Sans and Jevil. Sans' laid - back yet perceptive nature combined with Jevil's chaotic and unpredictable personality would make for some really interesting exchanges. Sans might try to understand Jevil's view of the world, which is so different from his own in Undertale.
Susie and Undyne would be a great pair. Susie is the tough - looking monster from Deltarune, and Undyne is the powerful fish - like monster in Undertale. They could have an epic battle at first, but then realize they have a lot in common. They both have a strong sense of justice and a love for fighting. After their initial clash, they could team up to fight a greater evil, perhaps something that threatens both Deltarune and Undertale. They could exchange fighting techniques and learn from each other's strengths.