They might be characters from a specific genre of story. For instance, if it's a romantic comedy, Sonny could be a bubbly girl and Chad a bit of a shy but charming guy. They could be neighbors or coworkers, and their relationship develops in a humorous and heartwarming way.
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.
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.
Sonny might become more confident in her relationships. The kiss could make her realize that she can be bold in matters of the heart. Chad, on the other hand, might become more vulnerable. He has always been a bit of a ladies' man, but this kiss could change his approach to relationships.
Sonny might be a werewolf pup who has a problem with Mommy, who could be Leah as a mother - like figure in the werewolf pack. The 'shut up' comment could stem from Sonny's disagreement with Mommy's decisions regarding pack matters, like how to deal with the vampires in their territory.
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.