Well, clearly Jim and Tim are main characters. They are the ones the fanfiction likely focuses on in relation to the Kim Possible universe. They are known for their inventive and sometimes zany ideas.
There could also be villains from the Kim Possible series that play important roles. For instance, Dr. Drakken or Shego. They might be the antagonists that Jim, Tim and Kim have to face off against, which can drive the plot forward and create interesting situations for the characters to navigate.
One idea could be that Jim and Tim create a new invention that accidentally causes chaos in Kim's crime - fighting world. For example, it might disrupt her communication devices during an important mission.
Friendship is a common theme. Jim and Tim often rely on their bond to get through various situations. Another theme is adventure, as they are usually depicted going on exciting escapades.
Well, there's a fanfiction titled 'Jim and Tim's Extraordinary Day'. In this story, they discover a hidden talent within themselves while trying to solve a local mystery. It's a really engaging read. There's also 'Jim and Tim in the Parallel World' which explores what would happen if they were in an alternate universe.
Obviously, Kim Possible would be one of the main characters. She's the star of the original show, so in the fanfic she would still be at the center of the action. Ron Stoppable would also likely be there. He's Kim's sidekick in the original series and would probably play a similar role in the fanfic, providing comic relief and some backup during the gaming - related adventures. Rufus, Ron's naked mole - rat, might also make appearances, perhaps with some new abilities or quirks related to the gaming world.
Well, Naruto himself is often a popular choice in these crossovers. His determination and powerful ninjutsu make him an interesting addition to any story with Kim Possible. He can bring a whole new level of action to the story.
Kim is an obvious choice. She's the main character and her skills, determination, and quick thinking can be explored further in mind - game scenarios. For example, how she adapts her physical combat skills to deal with mental challenges.
There could be a time - guardian character. This character could be an ancient being that has been protecting the timelines and appears to help Kim understand the true nature of time - traveling and the rules she must follow to set things right.
A new character could be introduced as the main antagonist. Maybe a powerful alien who sees Kim's new powers as a threat to his plan of taking over the earth. This alien could have his own set of powers that are quite different from Kim's, like the ability to control minds. Kim would have to not only learn to use her new powers but also find a way to defeat an enemy with such a dangerous ability.
Shego could also be the main antagonist. Maybe she discovers a way to time travel on her own and decides to go back in time to eliminate Kim before she becomes a threat. Kim would have to follow her through time to prevent this and save her younger self.
It could be an evil scientist who wants to capture the cat girl for her unique abilities. Maybe he wants to use her enhanced senses or agility for his own malicious purposes.