Two of my all-time favorite Doctor Who episodes are "The Pirate Planet" and the first one with Pertwee, "Spearhead from Space". Not because they're the best Doctor Who episodes ever made (I think "The Pirate Planet" still holds up. It was written by Douglas Adams, after all.) but because they were the first two episodes I ever saw. And at the time I didn't have a clue as to what the hell I was watching. The first time I viewed both of them I wasn't tuning in to see Doctor Who, I was just flipping through the channels. I came in partway through both times and had no idea what I was watching. It was years later before I knew the name of the show. By the next time I was able to see both episodes I owned like a hundred Doctor Who books, had a dozen episodes on tape, and for a short period I even wore a stupid scarf. Why? Because the wonderment of not knowing what the hell was going on energized me.
To bottle that magic, that sense of wonder, for gaming really only requires a little bit of work. To produce wonder you first must show the players that the campaign world is bigger, grander, more horrible, or more beautiful than they expect. To do this the GM simply must be prepared to go off script from time to time. Don't be a slave to the sample magic items or setting info or monster stats. Just don't overdo it. One kobold with a laser pistol is enough. Where did it come from? How did the goblin get it? Later, when they see a metallic wedge flying at high speed overhead, maybe they will get that it's a spaceship. Maybe they won't. Don't be afraid to leave little bits like this dangling. Ignorance is the stepping stone of wonder.
Incidentally, this need for ignorance probably goes a long way to explain my reaction to later Star Trek series and Joss Whedon's Firefly. By the time I encountered Firefly or Voyager I felt jaded, like I knew everything that was going to happen in each episode.