In the second chapter of I Am a Cat, we see this:
SINCE New Year’s Day I have acquired a certain modest celebrity: so that, though only a cat, I am feeling quietly proud of myself. Which is not unpleasing.
On the morning of New Year’s Day, my master received a picture-postcard...
I Am a Cat, chapter 2
We see that the cat is pretty well known; almost all of the letters and stuff that we see the master receiving mention the cat.
But don't see any mention of how this cat became well-known. Did I somehow miss it? What happened?