Yes, its not unfamiliar scenario to me too. The animal "allergy" with my inlaws is actually intolerance and a way of trying to annoy me. And then there are the arguements about smoking in the house....
Most annoying was this summer, four days notice, but we had a party which we had to cancel (no way was my sil going to be rude to MY friends, lol) and a dinner party. The unannounced visit was reason number one for accepting a posting in Italy and leaving London, italy being even further from NYC, lol!