Maybe a story about a little girl who found a pair of big black boots in her attic. They were magical boots that could take her to different lands when she clicked her heels together.
The phrase 'black cat boots off fanfiction' is quite puzzling. It might be an inside joke or a very specific reference within a small group of fanfiction writers or readers. For example, perhaps there is a particular fanfiction series where a character who owns a black cat and wears boots does something that has a major impact on the fanfiction world, like shutting down a major plotline or causing a shift in the story's direction. Without more information, it's difficult to determine its exact meaning.