Technically and scientifically speaking, there is not an actual, living human being on Earth who has proven wholly they know what an alien looks like. Many of us have the same basic core ideas of what we THINK aliens look like in our minds (little gray dudes with big, onyx eyes, etc), but why is that?
If no one has seen one (in a way that can be proven), why do we imagine aliens to look the way they do, when in fact, what they look like could actually BE so alien to us, we would have no frame of reference for it. Hell, that is what most of H.P Lovecraft’s work is about. Abominations from beyond the galaxy so hideous and monstrous, people go MAD when they gaze upon them.
But the reason we all picture aliens the same way is simple once it all gets laid out for you like it does in the following video:
So honestly, you actually have no frame of reference for what an alien would look like and what we imagine when we think of them in our mind’s eye we imagine because it has been programmed into us over time via film, movies, books, and pop culture in general.
So rest assured, if or when you do get abducted and do get probed, the thing probing you may look like nothing your (or anyone’s) eyes may have ever seen.