I don’t believe stories about aliens capturing isolated nutters and probing them on their spaceships before bringing them home, but who don’t bother to make their presence known to anyone else. That makes no sense. I theorized many years ago that perhaps the main reason we don’t see aliens visiting is that by the time a civilization gets to the technology level that permits interstellar travel, they are most likely to eradicate themselves via high-tech weaponry, nanotech accidents or some other tech-enabled extinction route. I suggested that almost all civilizations would become extinct within 300 years of discovering radio.
I also wrote a blog about how genetically engineered fairies would make ideal space travelers, since they could be made very small, and therefore only need small and cheap space ships, but thanks to electronic brains or use of external IT as brain space, be just as smart as real people, and have wings to fly around zero gravity spaceships.
Extending that thought to what aliens might look like, they would likely have the same capability in genetic engineering, and face the same engineering constraints, so would likely come up with a similar solution.
Miniaturization could go much further, and it’s possible in principle to make tiny capsules, microns across, that contain all the data needed to make a human or android body, and a few nano-fabricators that could do the building of other fabricators that make the infrastructure, robots, androids and organisms once they land on another planet. Maybe an advanced civilization might have the technology to make small wormholes through which to fire these tiny capsules in many directions so as to rapidly explore and colonize a galaxy. Given reasonably expectable morality, they wouldn’t want to geoengineer planets that are already inhabited, so the capsules would only activate if they land on uninhabited planets.
So, given these two quite likely technology capabilities for an interstellar space-fairing civilizations, aliens would either be in a micron-sized capsule or two that could be anywhere on the planet, and therefore highly unlikely to ever be found… or they might look like fairies.
Many people through history claim to have seen fairies of various descriptions, and usually they have magical powers. Via Arthur C Clarke, we of course know that any sufficiently advanced technology looks like magic. So, although I don’t believe they exist or existed, and think that those who claim to have seen them probably have poor eyesight or overly vivid imaginations or are drugged or pissed, or hallucinating, there is a small but finite possibility that they have existed and were visiting aliens.
Maybe fairies, pixies and other magical tiny people were simply aliens from different star systems.