[Fyron]

With the buttered toast strapped butter-up to the cat's back, it will always try to invert the cat so that it lands buttered-side down. The cat will always try to invert so that it lands feet first. Neither will ever be able to happen.

If you put the toast on the cat's feet, both will orient in the same direction, resulting merely in falling. Of course, if the butter is facing upwards towards the cat's belly, you will either have the same affect as strapping it to it's back, or the legs will break and contort into odd angles so that the buttered side lands face down and the cat lands on its feet simultaneously.