Let me preface this by saying that I'm fairly obsessed with PKD, to the point where I read all three volumes of his personal letters. Its no secret that his body of work was original, inventive, and hugely influential. One point of pride that PKD bragged about in several of his letters was his "invention" of the sci-fi trope in which an android doesn't know that it's an android. So far as I am aware, the story "Impostor" is the first example in fiction of an artificial construct believing itself to be a normal human being, and this trope has since been repeated countless times, as recently as Terminator Salvation and Black Mirror.

The release of Amazon's new PKD show "Electric Dreams" inspired me to re-read the stories that they chose to televise (collected for your convenience in a new book of the same name called Electric Dreams), and re-reading them made me consider some other tropes that have been invented or at least popularized by PKD. The first is the alien body-snatcher... Jack Finney's "Invasion of the Body Snatchers" was released in serial the year after PKD's short story "The Hanging Stranger" which has a very similar plot aside from the lack of seed pod incubators (Finney's seed pod inspiration can be attributed to the 1951 film "The Thing from Another World" which involves alien seed pods but no possession of human bodies). Can anyone think of an earlier "body snatcher" type story than The Hanging Stranger (1953)?

I also re-read PKD's "Impossible World," which involves future humans landing their spacecraft on a random barren planet, scamming an old lady into thinking the planet is Earth. In the end we find out by implication (an American coin) that the planet was in fact Earth. This story predates "The Planet of the Apes" as well as the Twilight Zone episode "I Shot an Arrow into the Air." Can anyone think of an earlier story in which astronauts land on Earth but don't know that they're on Earth?

What other Sci-Fi tropes can you think of that PKD may have invented?