Written by a kid fresh out of college (with an uncredited rewrite by Gene Coon), this comedic ensemble episode is arguably the most popular, memorable, and best TOS episode, appealing to hardcore, casual, and non-fans of Star Trek alike.
Taking advantage of the cast's natural chemistry, Gerrold's tight script features rich character interplay that develops its humor organically from the situations and relationships in a way that makes us love the characters even more. With such crisp writing as the backbone for scene after scene, "Tribbles" creates the illusion of one cohesive story, though Gerrold cleverly hides an A/B plot structure beneath the surface. On the one hand, we have Kirk navigating a bureaucratic and diplomatic mess, a TOS trope that always works because it's easy to contrast our active, action-oriented captain with pompous, desk-bound, mealy-mouthed paper pushers. (William Schallert, who would pop up on DS9 some 26 years later, fills the latter role quite nicely as Federation Undersecretary Nilz Baris). On the other hand, we have the rascal, Cyrano Jones (a Harry Mudd-like character brilliantly played by Stanley Adams), and his tribbles, the latter being the most brilliant gag a Star Trek writer has ever developed. Their triple advantage is A: they work in the script as a legitimate threat, B: they work on screen as a striking visual that gets funnier and funnier as the episode moves along, and C: They work for free, costing only the price of a roll of carpet.
With the two plots seamlessly interwoven and a Federation/Klingon bar-room brawl tossed in for good measure, "Tribbles" gives the series a unique sense of fun while remaining true to the characters and ideals that make TOS special. For the Star Trek cast, there would be many difficult times to come, with script and budget problems threatening to crush their spirit; but for this brief moment, you can tell that they're having the time of their lives, with only Leonard Nimoy able to (barely) keep a straight face. Given the chance to lighten up and have some fun, the ensemble gives one of their best performances, showing off an underrated talent for comedy that often gets buried in drama. Like Shakespeare, the actors have an uncanny knack for alternating between fun and seriousness, an asset that comes more into play in the feature films. In the meantime, "Tribbles" takes Kirk and the tribbles and combines humor and heart to give us a story with near universal appeal.
Captain Koloth, originally meant to be a recurring character, returns in the same episode and also appears in DS9's second season episode, "Blood Oath". But upstaging these and just about everything Star Trek has ever done, "The Trouble With Tribbles" itself comes back in "Trials and Tribulations", a DS9 fifth season episode that features Sisko and company travelling back in time to rub shoulders with Kirk and Spock and includes a cameo by David Gerrold himself
Remastered Version: With DS9's "Trials and Tribulations" preceding the upgraded version of "Tribbles" and featuring all new shots of the Enterprise and the space station she visits, this is a unique case where CBS Digital arrives late to the party. This means that CBS, to save money, could just lift some shots from DS9's episode. The CBS team, however, decides to create everything from scratch.
Most of the shots are similar to their original counterparts, which are quite well done for 1967. (It's interesting that TOS would even go to the expense of doing a space station here, because the action could just as easily happen on a planet, with a stock planet sphere and stock matte painting providing the setting for free. Gerrold, of course, was a rookie and wrote the station in without thinking of budget. The real surprise is that the show didn't change it, especially considering every episode after this uses preexisting footage of the Enterprise).
The space station itself presents the episode with a unique opportunity: a chance to show the Enterprise off in the distance through a window. The original version achieves the effect simply and cheaply by hanging an AMT Enterprise model against the backdrop. The problem? It doesn't move, despite exterior shots showing that it should. The updated version removes the model and adds a realistic Enterprise that can be seen graciously moving from one side of the window to the other.
Lastly, whereas the original version excludes the talked about Klingon battle cruiser (being one element too many for the compositors), the upgraded version, like "Trials and Tribulations", is sure to include it.