What are some interesting plot ideas for 'traveling the world with you fanfiction'?

One idea could be exploring the wife's time travels to different historical events not shown in the original. For example, she could travel to the signing of the Declaration of Independence. Another could be a story where the husband also gains the ability to time travel briefly and they have to figure out how to manage their travels together. And perhaps a plot where the wife travels to a future time and sees how their relationship impacts future generations.

One idea could be to have the girls go on a new adventure outside of the countries they've already visited in the original story. Maybe they find a hidden message in the pants that leads them to a mysterious island. Another could be that a new girl somehow gets involved with the pants and the sisterhood has to decide whether to let her in or not. And they could also face a situation where the pants get lost in a really strange place and they have to rely on their friendship more than ever to find them.

One idea could be a modern - day person suddenly being transported into the Naruto world and having to learn chakra control from scratch. They could struggle with the cultural differences and make friends with some of the original characters like Naruto or Sakura while trying to find a way back home.

A third idea could be a quest within the new world. The characters hear about a powerful and mysterious artifact that has the ability to grant a single wish. They embark on a journey across different regions of the new world, facing various challenges and meeting new allies and enemies along the way.

One plot idea could be that Ichigo goes back in time to the moment before a major battle in the Soul Society arc. He uses his knowledge of the future to prevent certain casualties and change the course of the battle in a more favorable way for his side. Another idea is that he travels back to his own childhood and tries to understand his powers better from an earlier age, which could lead to him becoming even stronger in the present. Or perhaps he goes back to a time when the Hollows first started emerging in large numbers and tries to find the root cause of their sudden increase, which could potentially change the whole history of the Soul Reaper - Hollow conflict.

Maybe Ash and his Pokemon travel to a parallel dimension where the rules of Pokemon battles are completely different. In this dimension, Pokemon can combine their powers in unexpected ways. Ash has to quickly adapt and learn these new battle styles in order to compete in a grand tournament there and find a way back to his own dimension.

You could also write a fanfiction where one of the girls loses the pants. Panic ensues among the sisterhood. They embark on a journey to find the pants, and during this search, they learn more about themselves and the true meaning of their friendship, which is deeper than just the pants.

One idea could be Hiccup discovers a hidden tribe in a remote jungle. Another could be that he encounters a mythical creature in an uncharted ocean region. Maybe he also teams up with a group of international dragon riders to save a world - spanning dragon sanctuary.

One idea could be a story where the protagonist discovers a new type of Pokemon that has unique powers and is being hunted by an evil organization. They have to protect this Pokemon and find a way to make the world accept it.

One idea could be Sonic getting stuck in an alternate dimension within the Lost World and having to team up with some of the local creatures he usually doesn't interact with to find his way back. Another could be a story where Tails discovers a hidden power within the Lost World that could potentially save Sonic's life when he's in a really tough situation against Eggman. Or perhaps a fanfiction where the Lost World starts to merge with Sonic's normal world and he has to figure out how to stop it before chaos ensues.