I, too, have had the problem of pissy cats. Usually, they were no longer kittens when I adopted them, or there was already another cat around causing terrirorial problems.
There is a product on the market that you can buy at most any pet store (sorry I forget the name, but the sales staff will know what you mean). In severe cases you cage the cat in a large crate with his litter pan with that special stuff sprayed in the pan. After that, you can confine him to one room with treated litter pan. After about a week, you let him into the rest of the house, but still treat the litter pan. Worked like a charm for me.
Say, maybe we SHOULD have a pets' forum!
