The original Star Trek is undoubtedly one of the most recognizable TV shows of all time. The colorful costumes, memorable characters, and thought-provoking stories all worked together to create a phenomenon that shaped our culture in unexpected ways. As subsequent shows set in the Star Trek universe began to emerge, it was safe to say that Star Trek had contributed its own unique legacy to the television landscape.
What a lot of people may not realize, though, is that Star Trek's legacy could have looked much different than what we know today. In the early days (and sometimes later days) of the show, a lot of the history and world-building was a work-in-progress. As a result, something that was established in one episode might be retconned in a later episode.
Looking at some of Star Trek's biggest retcons gives an interesting insight into the show's past as well as a future we never got to see.
Shuttlecrafts are often used as an alternative means of transportation. They are especially useful for survey missions to newly-discovered planets. But in some of the early episodes, they are conspicuously absent.
The best example of this appears in The Enemy Within. A landing party is trapped on a planet where the temperature is plummeting dangerously low, but they can't be transported up because of a malfunction that split Kirk into his good and evil halves. In spite of the life-threatening temperatures, though, nobody suggests sending a shuttlecraft down to get the landing party. In fact, there's nothing to suggest that shuttlecrafts even exist. Only in subsequent episodes do they begin to appear, and everyone acts as if they've always been around. But if the shuttlecrafts were always around, why didn't they use them earlier?