Works well until they get bored and decide to face in the other direction.

Try it yourself. You'll see the problem!

Had to go back to the litter tray.

Looking back now, I wonder was it a silent protest against the humiliation. Never underestimate a cat's intelligence.

I've heard of a cat who crapped only in the slipper of the father of the household.

Another one, a Tom, used jump across the doorway from the top of the wardrobe on one side of the doorway to a shelf on the other side whenever anybody was coming in the door. Peeing copiously as he went!

A new take on Dante's 'Abandon Hope all Ye Who Enter Here'. And now I come to think of it, he was an Italian cat. Fiscio, by name.