For a long-running series like Star Trek to keep people interested, it has to find ways to reinvent itself to stay relevant. Think of it as the Cher of SciFi franchises, surviving eternally despite some fairly major setbacks along the way. One thing Star Trek has developed is a pair of cajones, giving it the guts to change up the game from time to time.
As can be expected, not all of the risks and twists that it takes are met with universal acclaim. In fact, in the history of television, has there ever been an episode of any franchise ever that has had every single viewer love it? It's an impossible task to achieve, so the world needs entries like the ones on this list to switch directions when needed.
Explosions are great, time loops are fun, and stigma-shattering storylines are a hoot. But overall, keeping the spirit of the franchise alive while it does things that make your grandparents squirm is one of the main reasons that almost sixty years later, people are still talking about and giving out about Star Trek.
10. The Changing Face Of Evil
If there was one thing that was certain in the various TV series of Star Trek, it's that the main ship is never destroyed (permanently). There is always a failsafe or a last-minute escape route for the famous crews. The Changing Face Of Evil, a seventh-season episode of Star Trek: Deep Space Nine, took this and used the audiences' expectations to make the destruction of the USS Defiant truly shocking.
Ira Steven Behr, having already killed Jadzia Dax, understood the power of a crippling defeat against the good guys. So, when the Federation heads to the Chin'toka system to retake their only foothold in Cardassian space, he knew that a big loss would be the only way to convey the threat of the Dominion and their new allies the Breen to the audience.
How many times had the show depicted the USS Defiant heading off to battle, taking beating after beating, surviving despite it all? Even Star Trek: First Contact saw the Defiant survive the Battle of Sector 001, a deadly confrontation with the Borg that left dozens of other starships destroyed.
So, when the Breen strip her of all of her power with their first shot before the Jem'hadar quickly finish the job, not one person watching the television saw it coming.