Second Variety:
https://en.wikipedia.org/wiki/Second_Variety
The Father Thing:
https://en.wikipedia.org/wiki/The_Father-thing
The Hanging Stranger:
https://en.wikipedia.org/wiki/The_Hanging_Stranger
Do Androids Dream of Electric Sheep:
https://en.wikipedia.org/wiki/Do_Androids_Dream_of_Electric_...
Quite a few, actually! Fake humans were his specialty.
Philip K. Dick and the Fake Humans:
https://www.bostonreview.net/articles/henry-farrell-philip-k...
>"the bombardment of pseudo-realities begins to produce inauthentic humans very quickly, spurious humans—as fake as the data pressing at them from all sides. My two topics are really one topic; they unite at this point. Fake realities will create fake humans. Or, fake humans will generate fake realities and then sell them to other humans, turning them, eventually, into forgeries of themselves. So we wind up with fake humans inventing fake realities and then peddling them to other fake humans." -PKD
I'd give you a million to one odds against that. More precisely to operationalise: against that being discovered to be the case in the next twenty years.
The way evolution and biology works, what you are suggesting is extremely unlikely. (See https://www.lesswrong.com/posts/pLRogvJLPPg6Mrvg4/an-alien-g... for a start of an explanation.)
Also, it was a bit of a whimsical fantasy rather than some serious theory I have about the world. In any case, even if such beings were to exist, I suspect we'd not be able to detect them any more than the termites would be able to detect the beetle. We probably wouldn't have the faculties to comprehend and apprehend the nature of the being, any more than an ant could understand general relativity.
It's kind of tiring having habitual iconoclast skeptics come out of the woodwork with some superficial dunk every time something out of the ordinary but also of no real consequence is said.