There's a humpback whale in my back yard!

It was approaching my son's fifth birthday, so I asked him what he wanted. "A humpback whale," he stated. I sputtered as he gave me a look of full assurance that I would be able to run down to the pet shop and pick one up in little baggie. "Where are you going to keep it," I asked politely. "In the yard." He had obviously given it some thought, but I felt that he lacked some reference to the size of a humpback whale. So I explained that even a small whale would be bigger than our house and it wouldn't fit in the yard. He threw the logic back in my face. "But Dad, we could put it in the back yard."