Kitty Norville, based on the title, is the character who is going to save the world. She could be a normal person thrust into extraordinary circumstances, or perhaps she has some pre - existing skills or knowledge that make her the ideal candidate for this world - saving task. We can't know for sure without reading the book, but she's clearly the focus.
I'm not sure exactly as I haven't read it. But from the title, it seems that a character named Kitty Norville is involved in an adventure where she saves the world.
The 'bunny bunny' in 'bunny bunny gilda radner a sort of love story' is quite mysterious. It might be something that was special between Gilda Radner and another person in the story. Maybe it was a term of endearment, like a cute nickname. It could also be related to an inside joke or a shared memory that was important to the love story. Without more information, it's difficult to determine its exact significance.
Kitty drew a big castle by the sea. The castle had tall towers and a drawbridge. Then Kitty told the story. There was a princess living in the castle. She was kind but lonely. One day, a mermaid came to the shore near the castle. The princess and the mermaid became friends and they had many adventures together, exploring the sea and the land around the castle.
Hard to say for sure. Hello Kitty has become such a big brand with various interpretations and tales. Some might have elements of truth, but many could be just made up for entertainment.