Here's something I've been curious about. How many pre-existing Science Fiction stories have been adapted into Star Trek episodes? Also, what stories would you have liked to be adapted into Star Trek? (All Series are welcome.)
I personally think a re adaptation of Fantastic Voyages would have made a pretty cool TOS episode. It came out around that era but it would have fit well into TOS. Heck even Immunity Syndrome had exploration into a single cell organism so it's not to far off.