The old woman screamed at her husband that he needed a brain transplant. He popped open another beer and asked who would serve as donor. She answered that she would, of course, since she was the only one in the household with a brain. As the man mulled this over, his wife reminded him that couples had the best chances of success with transplants. He nodded and agreed to her proposal — provided she threw in her liver. She smiled in assent, pleased with herself, though vaguely worried that the next time she wanted something, her husband might be of an altogether different mind.