10 Best Star Trek The Original Series Episodes

8. The Trouble With Tribbles

Although The Original Series never lacked some cheap alien critters (Kirk's pet unicorn-wearing pooch comes to mind), the Tribbles take the cake.

The furry fellas in question jumped on to the scene in 1967, and have been one of Trek's most enduring creations ever since. They're the definite highlight of the episode in question, but Trouble's genius lies less in its use of the aliens, and more in its approach to a burgeoning cosmic crisis.

Focused on a territorial dispute between the Klingon Empire and the Federation, the episode divulges duplicity on both parties' behalf, adding the Tribbles in as another headache to the already fraught negotiations underway.

As far as Trek episodes go, TTWT is perhaps the most iconic. It's emblematic of a Sci-Fi era where creatures themselves always looked less than convincing, but as far as images go, they don't get any better than Kirk engulfed by a sea of abandoned wigs.