"Cats are intended to teach us that not everything in nature has a function." — Garrison Keillor
Take this leather three-seater couch, for example. The owner's elderly cat had taken to using the seat for a toilet on at least a couple of occasions. The damage caused by the cat's urine was significant, contaminating not only the leather and adjacent synthetic materials, but also the foam, the wooden frame, and even the metal bolts!
Remedial work involved replacing the contaminated leather and foam, as well as treating the wood and replacing the corroded bolts, among other things. Finally I recoloured the replacement leather to match the existing. Fortunately, our client's insurance company came to the party. And the cat? It had used up all of its nine lives.