One day I was in my philosophy class, and my teacher was talking about some theory in which everything was the same. It was really odd, he kept asking questions like "What is the difference between paper and a tree? You can make paper out of a tree." After some more examples, like "What is the difference between a window and a door?" I was getting rather annoyed. So, when he asked "What is the difference between spam and eggs?" I blurted out loudly with confidence that "They taste different!" At this, the whole class, including the teacher, bursts out laughing. They don't stop laughing for about five minutes, and meanwhile the teacher has collapsed on his desk pounding it with his fist and trying to breathe. Turns out, he had asked the difference between sperm and eggs.