I found something on wikipedia and it posed a very good point. When someone tries the experiment and it is a failure it could simply be because of the following:
Another theory is that as the cat is dropped and begins to rotate at
a very high speed, the butter will begin to fly off of the toast, until
it is all removed. Once the butter is removed, the cat will simply fall
to the ground on its feet, as the piece of toast on the cat's back is
now butterless.