What are some interesting plot ideas for a 'Basil the Great Mouse Detective' fanfic?

An OC who is a street - smart mouse with a network of informants all over the city could be interesting. This OC could come across a strange occurrence that they think Basil should know about, leading to a new adventure. They could provide Basil with valuable leads from their connections on the streets.

You could introduce a brilliant mouse scientist who has created some newfangled gadget that could help Basil in his detective work. Another good character could be a mysterious mouse from a far - off land who has some valuable information about the case but is very secretive. And a street - wise mouse informant who knows all the gossip and rumors in the city would also be great.

One idea could be a crossover with Sherlock Holmes in the human world. The great mouse detective could team up with Holmes to solve a mystery that spans both the mouse and human realms. Maybe there's a villain causing chaos in both worlds and their combined skills are needed.

The OC could be from a different part of the mouse world with unique skills, like being able to communicate with certain insects that can help in solving crimes. For example, they could get information from a spy spider about a villain's lair location. The OC then teams up with the great mouse detective to use this new lead to solve a big case.

Another plot could involve a detective in the series, perhaps a side character, who is pregnant and uses her unique situation to solve a case. For example, her pregnancy hormones might make her more perceptive in some ways or she could use the fact that people underestimate her because she's pregnant to her advantage in uncovering the truth.

One idea could be exploring the backstories of minor characters during the Great War. Maybe show how they got involved and what their personal stakes were.

One interesting story could be about the great mouse detective solving a mystery in an old, abandoned cheese factory. The clues are hidden among the cheese wheels and old machinery.

One idea could be a mouse that has magical powers and becomes friends with Harry. It could help him in secret ways, like finding hidden passages in Hogwarts by squeezing into tiny holes that humans can't reach.

One idea could be exploring the untold stories of the soldiers on the front lines. Maybe focus on a small group who are trying to complete a secret mission during the chaos of the time war. Another could be delving into the origin of the time war and how it could have been prevented from the perspective of a time - traveling historian.

One idea could be a fanfic where Conan has to solve a mystery within a virtual reality game world. Another could be a story where he teams up with a new character who has a unique detective skill that complements his own. Maybe a fanfic about Conan traveling back in time to solve a mystery related to his parents' past.