The "butter-side down" thing is a special case of Sod's Law, while the feet-first thing is a special dispensation of the God of Cat-kind. It's not a good idea to mix natural and supernatural laws; the only thing you can guaratee is that it'll end in tears!

Anyway, Sod's Law is recursive: if you try to make you bread land butter-side down, it won't do it.

Seriously, now: don't try and feed gasoline to your cat; regardless of whether the cat kills you, you'll certainly kill the cat. I kid you not.

Steve