When I was younger (1970s child), some zoos would actually sell some of their surplus animals-usually domestics from the pet's corner. Did anybody ever get something a bit more exotic? I can imagine for example, walking out of Southampton Zoo with a chimp on a lead, given the owners and the purpose of the place!
Its happened a lot more recent than the 70's to Gary. I know of some within the last 10 years. Nothing as exhilarating as a lion on a lead of course, but some animals are equally suited to life in a large enough field with decent shelter, be it a zoo or not. If the care is good enough and the situation suits both parties, why not?