Adrien is the central figure here since he's the one acting like a cat. But other characters like his father could be involved too. His father might be worried or even angry about his strange behavior. And then there's Plagg, Adrien's kwami. Plagg could either be the cause of this change or be trying to help Adrien get back to normal.
Maybe Adrien got cursed and started acting like a cat. He might start chasing yarn, purring when happy, and rubbing against people's legs.
The main characters are clearly Adrien and his dad. Adrien is the one who has the cat puns to share, and his dad is the recipient of these puns.
It could be Ladybug. If Adrien turns villain, Ladybug would be the natural antagonist as she represents the good side. Their relationship would be completely flipped from what it was before. She would have to try to stop him from causing more harm, all while probably still having some feelings for the old Adrien.
Sasuke could be an important character. He might be initially confused and a bit annoyed by Naruto's cat - like behavior, but as the story progresses, he could start to find it endearing or even useful. Another character could be Kakashi. He would probably be the one trying to figure out what caused Naruto to act this way and how to reverse it, if needed.
It could be an old man and a young child who are both in a similar situation, like having a terminal illness. The old man has a lifetime of experiences to share, and the child has a fresh and innocent view of life. Their differences and similarities could form the basis of a beautiful friendship.
Obviously Naruto would be one of the main characters, with his fox - like chakra. Another could be a new character, a cat - ninja from a far - off land who comes to Konoha. They meet and form an unlikely alliance.
Perhaps the cat tail is a curse at first. Adrien has to deal with all the awkwardness it brings, like not being able to hide it properly. But as time goes on, he realizes that the tail gives him an edge in certain sports or activities, like climbing. So it turns from a curse to a sort of advantage.
May could be one of the main characters. She could join Ash on his journey and share her knowledge about Hoenn's Pokemon with him. Another could be Brock, still tagging along to offer his expertise in Pokemon care.
Well, perhaps Adrien has been reading a lot of cat - themed books or stories that are full of puns. He decides to tell his dad these puns to brighten his day. For example, he says 'Dad, I heard that cats are great at multi - tasking. They can nap and look cute at the same time!'. His dad might then join in and they could have a fun time coming up with their own cat puns.
Chloe could be the main antagonist. She has a history of being jealous of anyone getting close to Adrien, especially Marinette. So, she might set a trap for Adrien out of spite or to keep him all to herself.