I agree Tilly2
I think we saw the graduate cats.
And I didn't like the way one of them was whipping yards of loo paper down the toilet, our septic tank couldn't cope with that
Apparently you do it in stages and begin with draining the water out of your toilet and filling it with cat litter, then i suppose you keep reducing the amount of litter and then introduce water. I presume you'd need to have more than one toilet available for this stage unless you are happy to scoop your own *** out of the litter as well as the cats.
I can see that being workable though. Getting them to flush and then wash their paws is probably the hard part...