From the Original Series: The Mark of Gideon
TOS was very often both creepy and silly, exactly like Halloween. There’s something about the empty corridors of the Enterprise that feels extra spooky in this episode.
From The Next Generation: Conspiracy
Gross bugs! People shoot bugs, eat bugs, and host bugs in their chest cavity.
From Deep Space Nine: Necessary Evil
Other than being a little darker than other episodes, this one isn’t especially fitting for Halloween. We just think you should watch it on Halloween for the same reason you should watch it any other day: it’s a really good episode.
From Voyager: Macrocosm
Janeway fights to retake the ship from weird flying monsters!
From Enterprise: Dead Stop
After sustaining terrible damage to the ship, the crew of the Enterprise stumble upon an un-maned automated repair station that seems too good to be true. This is one of our favorite Enterprise episodes, and one of the creepiest, just by way of being one of the more tightly plotted suspense episodes of Trek.