Another possibility is a crossover with "Star vs. the Forces of Evil". Star's magic wand and her somewhat chaotic personality along with Wander's positive energy would make for an interesting dynamic. They could work together to stop some sort of inter - dimensional threat that endangers both their worlds.
One idea could be a crossover with 'Steven Universe'. Wander and Sylvia could visit Beach City and interact with the Crystal Gems. They might get involved in one of the Gems' battles against a Homeworld threat and use their own unique skills to help out.
Maybe a fanfiction where Wander has lost his memory. Sylvia has to help him remember who he is while also protecting him from villains who want to take advantage of his vulnerable state. This could involve visiting old friends and places from Wander's past to jog his memory.
Perhaps a plot where the little bits create some sort of chaos in the universe, and Wander has to use his unique brand of kindness and problem - solving to set things right. He might have to convince the little bits that their actions are causing harm in a gentle way.
Once you have the characters and the meeting situation sorted out, start planning the plot. It could be a simple adventure where they have to retrieve a lost item that has ended up in the other world, or it could be a more complex story about saving both worlds from a common enemy. Just make sure to keep the essence of Wander Over Yonder intact while incorporating elements from the other universe.
I'm not sure specifically as it could be any number of things. It might be a fan - created story that combines the 'Wander Over Yonder' universe with elements of the Death Star from 'Star Wars'. Maybe it's about Wander and his friends having an adventure on or related to the Death Star.
The fanfic offers a different perspective on the show. In the original series, their relationship is more of an antagonistic one. But in fanfics, writers can transform it into something more complex and multi - faceted. It gives fans the opportunity to see what could happen if these two characters were to develop a deeper connection, whether it's a friendship based on mutual understanding or a more unexpected emotional bond.
Another good one is 'Redemption of Dominator'. This fanfic focuses on the idea of Dominator's possible redemption through her relationship with Wander. It delves deep into her character, showing her more vulnerable side and how Wander's kindness might influence her to change for the better.
One popular 'Wander over Yonder' fanfiction story could be those that focus on Wander's further adventures in uncharted galaxies. For example, there might be a story where he discovers a planet full of musical creatures and has to use his charm and kindness to make peace between them and a group of noisy invaders. Another could be about Hater finally realizing the error of his ways through an encounter with a wise old being in a fanfic, which gives a different take on his character development.
If it's a crossover with 'My Little Pony: Friendship is Magic', Twilight Sparkle would be a great addition. Her studious and sometimes overly - serious nature would contrast well with Wander's laid - back approach. And the ponies' world of magic and friendship could be an interesting backdrop for Wander and Sylvia's adventures.
One popular theme is friendship. Characters like Wander and Sylvia often have their bond explored further in fan fiction. Another theme could be adventure in different parts of the universe they travel. For example, fan writers might create new planets with unique challenges for them to face.