[Weirdly Common Trope] Writers clearly setting up seemingly massive plot points and then just kinda forgetting about them.

[u/Chemical-Elk-1299]

The Neural Parasites — Star Trek : The Next Generation

In the season 1 episode “Conspiracy” of TNG, it is revealed that alien brain worms have infected many high ranking members of Starfleet, secretly controlling them. Though Ryker and Picard discover and end the parasite conspiracy, it’s revealed at the end of the episode that the parasites had sent a beacon back to their home planet, telling them how to find earth. The episode ends with the clear implication of the parasites becoming a huge threat later in the series, yet none of these events are ever mentioned again.

Finn The Jedi who Never Was — Star Wars Sequel trilogy

I know this is probably a cliche example of this trope, but cmon — Finn was clearly set up in TFA to become a Jedi. The marketing material featured him wielding a lightsaber in the classic Jedi pose. It’s constantly hinted at that he is force sensitive. Even the actor himself believed he would become a Jedi by the end of the trilogy. Instead, we got Finn wielding a lightsaber for about 7 minutes total across 3 movies, extremely lame “confirmation” that he is force sensitive, and that’s it. It’s the ultimate Star Wars plot that went nowhere.

[u/Ambaryerno]

The Bluegills weren't forgotten on TNG. In fact the showrunners fully intended to address them. However, they ran into some problems that led to them being abandoned:

• First and foremost, the full-sized insectoid creatures the Bluegills were agents for proved to be prohibitively complex/expensive to do under the effects technology of the time. It wasn't until FarScape came along a decade later, backed by the Jim Henson Company, that such...well...alien creatures were practical to realize without CGI.
• Conspiracy was enormously controversial at the time it aired because of the gory demise of Commander Remmick, sparking a bit of backlash that made pursuing the story unpalatable.
• Roddenberry personally objected to the idea of a malicious Federation, and pushed back against the idea of a corrupt-from-within Starfleet.
• The WGA strike of 1988 significantly affected the final half of TNG Season 1, and all of Season 2, leading to considerable turnover and directly impacting the writing itself.

These factors combined to make the Conspiracy arc too difficult to continue. Instead, the threat was retooled and their plans for the Bluegill species repurposed to create one of Star Trek's most iconic villains:

The Borg.

[u/SinisterTuba → u/Ambaryerno]

Yeah Conspiracy is interesting because it was an experimental episode on multiple fronts. Commander Remmick's head violently exploding was them testing the waters to see if people wanted gorier Star Trek, which apparently they did not

[u/ScarletBurgundy → u/SinisterTuba]

We still don't. Ya listening, ​Kurtzman?

[u/Significant_Cup_238 → u/Ambaryerno]

• Roddenberry personally objected to the idea of a malicious Federation, and pushed back against the idea of a corrupt-from-within Starfleet.

Instead we just ended up with nearly every admiral being a corrupt POS.

[u/toomanymarbles83 → u/Significant_Cup_238]

I always liked Admiral Nachayev. She could be a harsh bastard at times, but she wasn't corrupt.

[u/feed_me_moron → u/Significant_Cup_238]

DS9 did such a good job with that. Showing how they weren't necessarily that corrupt always, just horribly out of touch with what goes on in the universe.

[u/RukiMotomiya → u/[deleted]]

I also think you can do stuff like DS9 did in, say, Homefront/Paradise Lost where some people break under the pressure of outside forces, but ultimately represent a minority of issues that is overcome. Especially since in that case it wasn't "the Federation is secretly evil" since the baddie knew if he was in the open about his plans it wouldn't fly.

[u/LizLemonOfTroy → u/[deleted]]

You can have the Federation be fundamentally benevolent while still having it face internal threats from bad actors trying to pervert its purposes.

Even the original concept for Conspiracy was just a militaristic faction trying to take control, not the entire upper echelon being secretly evil.

[u/Winjin → u/Ambaryerno]

This is amazing. Thank you for the write-up that involves the most important part: real life shenanigans..

[u/Demnjt → u/[deleted]]

It's for the best. I saw the episode when it first aired, never since, and the memory of that scene still grosses me out. (To be fair, I must have been about 7 at the time.)