That + you need to know Whitefire. Then meet hellcats a few times. That's all.
From what I tested it seems you need both Whitefire and a certain level of intelligence (not sure exactly how much though). They also have fairly strict requirements on what qualifies as a cat-morph. You need to be furred, for example, which is kind of odd because the combat event with the hellcat witch describes her as having skin. When I removed my fur I was only able to get the initial meeting event but not the rest, even though the appearance page still qualified me as a cat-morph.
Also, if you enter the transformation event with a small penis they don't grow it, but they do grow your breasts/hips/ass if they're too small, max out your femininity, and even change your body thickness/musculature to match the hellcat standard. Should probably change the event so it grows small penises too.
Last edited: