Sure. One great source could be fanfiction.net. They have a wide variety of stories featuring adena and kat. You can search by tags or simply type in 'adena and kat' in the search bar.
Once upon a time, the reader was walking in the neighborhood when they stumbled upon Mr Kat. Mr Kat was up to his usual antics, plotting against Kid. The reader, being a kind - hearted soul, decided to intervene. They tried to reason with Mr Kat, explaining that Kid was just a kid having fun. Mr Kat scoffed at first, but as the reader continued to talk, he started to listen. In the end, Mr Kat and the reader formed an unlikely friendship, and Mr Kat decided to give Kid a break.
Once upon a time, the Reader found themselves in the middle of the chaos between Kid and Mr. Kat. Kid was always up to his mischievous antics, much to Mr. Kat's annoyance. The Reader decided to try and mediate. They talked to Kid, explaining that Mr. Kat was just trying to keep things in order. Kid was hesitant at first but then started to listen. Mr. Kat, seeing the Reader's efforts, was also more open to Kid's youthful energy. In the end, they all found a way to coexist more peacefully.
I'm not sure specifically what that particular 1995 Casper and Kat fanfiction is about. It could be about their adventures in the afterlife, perhaps how they interact with other spirits or how they deal with the living world intruding on their ghostly existence.
One common theme could be friendship. Despite the 'vs' in 'kid vs kat', when the 'coop' and 'female kat' are involved, it might show how they can work together and form friendships.
Maybe in the fanfiction, there could be a parallel universe where Kid and Kat have different personalities. They are forced to coop to save both their worlds from destruction. Kat could be more heroic than usual and Kid could be more hesitant, creating an interesting dynamic.
One popular character to include could be Coop's sidekick or pet. It could add some comical relief to the story. Another might be a mentor - like figure who gives advice to Kid and Fem Kat during their adventures.
A possible plot could be that the Reader moves into the neighborhood where Kid and Mr. Kat live. The Reader is intrigued by the strange relationship between the two. One day, Kid accidentally breaks something of Mr. Kat's while trying to show off in front of the Reader. Mr. Kat blames Kid and they start arguing. The Reader steps in and suggests they work together to fix it. As they do, they start to understand each other more and the Reader helps them build a better relationship.
I'm sorry, I'm not aware of specific 'kid vs kat coop x female kat fanfiction' to recommend. You could try searching on fanfiction websites like FanFiction.net or Archive of Our Own.