So there we discovered something new in 2024!! An entire new type of lifeform is found , bacteria merged with algae and it created Nitroplast which takes nitrogen and converts it into ammonia, plants and alage need ammonia and they depend on bacteria for that, now this is like single cell version of Nitroplast, imagine a whole creature/animal evolved from Nitroplast(it will most likely take billions of years to evolve).
The supposed creature would intake nitrogen (and also oxygen/carbon dioxide optionally ), ofcourse if it creates ammonia inside of it, it's going smell bad, what if the aliens are not mammals or reptilians as we think?
What if aliens are evolved plants(doesn't sound impossible anymore), could it be reason that they show abductees and people who encounter them to be kind to earth and take care of our environment? It can also answer why they experiment us and animals, maybe they are completely different life form than us, and our bodies fascinate them to do research, who knows?
Discovery of Nitroplast gives us an idea that how much different lifeform can evolve and in how many different kind it can evolve, we have no idea how different kind of organisms may inhabited in this vast universe, it opens up to many possibilities!
Edit: evolving from plant can also explain why they are not afraid of dying, they may also lack survival instinct