In reference to this post
Honestly, it didn’t start off as anything that dramatic or angsty. There were a bunch of GIFs of David Tennant/the Tenth Doctor with cats, and a little streak of cute Zepheera-Visions came to mind. But that last part turned out much longer than I thought it would be when I started writing it, and I had no idea it would dive so deeply into Zepheera’s attitude toward the felines. It just happened, and looking back I don’t know where else this could have possibly gone.
As for the cats themselves, I assume they’re some alien race of psychic or telepathic cats who lure the Doctor into this bizarre state, and for whatever reason don’t affect Zepheera the same way. As of right now, this is the last appearance they’ll make, but who knows? Maybe in the future I will be motivated (or prompted) to write more about these felonious felines!