Tomorrow it could be an alien invasion.
Best put on clean underwear then. Nobody wants an alien anal probing with dirty underwear.
(PS. What is it with aliens and our bottoms? Is our poop essentially alien meth?)
I had a funny discussion with some friends about that during college. We were drinking and joking around and creating all sorts of stupid reasons for why aliens were conducting anal probes, but one guy had serious and interesting theory:
Human feces contain all of the body’s solid wastes. The solid waste is obviously composed of digested food but also dead cells of every type (blood, brain, heart, etc.), antibodies, antibiotics, viruses, bone marrow and everything else inside of us. If you want to gather a sample of everything inside the human body, the least invasive and quickest way to do that would be to extract a stool sample. And assuming they are indeed several hundred or several thousand years advanced in technology, it wouldn’t pose a problem for them to seperate the biological material from the feces and then study, catalogue or duplicate it for whatever purpose they want.
I remember that because we were having such a great time with lots of laughs and then he said that and everybody just got silent. It was a total buzz kill.