I'm going to do this as three posts for my own sanity.
The Trouble With Tribbles
This episode was written by David Gerrold, and it was his first professional sale, one of five script outlines he submitted to the producers. (His script was rewritten heavily by Gene Coon however) He also helped develop the story for the TOS episode The Cloud miners and he rewrote the episode I, Mudd, though he received no credit for this. He also proposed two episodes for series 3 that were never produced, but were reworked into the TAS episodes More Tribbles, More Troubles and Bem. The Trouble with Tribbles garnered a Hugo nomination, but it lost out to The City on the Edge of Forever.
Gerrold appeared twice of sorts in TAS: A security officer in More Tribbles, more Troubles was based on his appearance, and he voiced Em/3/Green in the episode "The Jihad". He would also have cameos in The Motion Picture and Trials and Tribble-ations.
Gerrold was one of the TOS writers asked to return to the TNG writer's room, and like Dorothy Fontana, he was a script editor, though he was not credited with any scripts during his time on the show. He wrote the novelisation of Encounter with Farpoint, much of the TNG Writer's bible, and he penned a number of columns about the production of series 1 for Starlog magazine.
He quit TNG about halfway through the production of series 1, partially because he had proposed an episode titled Blood and Fire which would have been an allegory for the AIDS epidemic, and included gay characters on the Enterprise. It was rewritten by Herb Wright as Blood and Ice (with the gay characters removed). But his primary reason for leaving was the interference of Roddenberry's lawyer Leonard Mazlisch, who forced out Dorothy Fontana (as I noted in my writetup of Yesteryear) as well as all the other TOS staff who had joined the TNG staff. Gerrold and Fontana held their silence on the subject until they were interviewed for William Shatner's documentary chaos on the Bridge, which once again, I highly recommend, and it's on Netflix.
He's also written for a number of behind-the scenes Trek books, and has been involved in the fan film scene, writing and producing for New Voyages/Phase II, and he has a producer credit on Axanar.
Outside of Trek, Gerrold write a number of novels, including the Star Wolf trilogy based on unused Trek ideas, including Blood and Fire (and has been described as Trek done right), and as-yet unfinished The War against the Chtorr series, a story of humanity's conflict against an alien ecosystem surplanting earth's. He also wrote for Babylon 5 (again, like Dorothy Fontana), Sliders, Land of the Lost and the Twilight Zone.
There's some continuity! In the opening scene, Chekov mentions the Organian peace treaty between the Klingons and Federation, which was imposed on the two nations by the eponymous aliens in the episode Day of the Dove.
George Takei doesn't appear in this episode as he was filming The Green Berets for a sizeable chunk of series 2's filming schedule. many of his scripted lines were transferred over to Chekov.
James Doohan did most of his own stunts in the bar room brawl sequence, and this episode marks one of the times you can see he's missing the middle finger on his right hand (he lost it during the battle of Normandy) - it's when he carries a bundle of tribbles saying they've infested engineering.
The bar set was first seen in Court Martial, and it was redressed somewhat here. There's also a lot of costume reuses in this episode. Eagle-eyed viewers will spot some early Starfleet uniforms, as seen in The Cage and Where no Man has Gone Before, and the miner outfits from Devil in the Dark in the bar.
While Arne Darvin, of course reappeared in Trials and Tribble-ations, Koloth also showed up in DS9, in the episode Blood Oath.
This is also one of the few episodes in which Scotty and Chekov have a conversation.
Some advertising tie-ins. Guy Raymond, who played the bartender was well known in the 60s for playing a long-suffering bartender in ads, who would comment on the weird happenings in his bar; and Ed Riemers, who played Admiral Fitzpatrick was a spokesperson for an insurance company. In an outtake, someone threw a Tribble at him and he caught it, going straight into his ad spiel.
Spock's estimate of how many Tribbles have bred in three days is 100% correct, but there were only around 500 Tribble props made for the episode. Most of them were just sewn out of carpet rolls, but the ones which could move had motorised toys hidden inside them. The props were very popular and rapidly vanished from the store room.
The miniature of the Enterprise seen from Lunny's office is actually an AMT model kit of the ship, as was commercially available at the time. Also, according to Michael and Denise Okuda, the production of this episode was the last time new model footage of the Enterprise was shot, although new scenes appeared in 5 episodes that came later in production order - so presumably they were shot earlier and were unused before those episodes.
There were eight takes of the scene where Kirk gets buried in Tribbles, which is an unusually large number. A few stagehands were behind the set, throwing Tribbles into the bin that was above Shatner's head on-set, to ensure it stayed as full as possible while the contents of said bin were falling out. But they couldn't see onto the stage from where they were, so they had no idea how many Tribbles were enough, There's a moment of genuine frustration on Shatner's face during the shot that makes it into the episode too.
While the episode was a big hit with the fans (and as I noted above, it netted a Hugo nomination), it had a mixed reception with the cast and crew. Shatner loved it, saying the big challenge was keeping a straight face, and director Joseph Penvey said he really enjoyed the change of pace and getting to do comedy with Shatner and Nimoy. In a 1985 interview, Penvey said that you could never do such a story in contemporary Trek, as it had become deathly serious. Of course, Star Trek IV would come out the following year, disproving his assertion somewhat.
Fan accolades include the episode being voted best in the Sci-Fi Channel's 40th anniversary fan poll, and Empire magazine saying it was the best episode when they did their best TV show countdown (Trek came 43rd overall)
However, Trek staffers including writer Samuel Peeples, Co-Producer Bob Justman, Series 3 Producer Fred Freiberger and Gene Roddenberry himself all disliked it to some degree. Series 2 producer Gene L. Coon wanted to introduce more comedy to the show and he and Roddenberry clashed frequently on the subject, leading Coon to quit the show and Freiberger to take his place. Freiberger would actively reject Gerrold's proposed sequel script (which became TAS' More Tribbles, More Troubles) for series 3, saying Trek wasn't a comedy.
And yeah, my thoughts:
So, this episode is a farce, and it indicates very early that we;re going for broad comedy. The pre-credits scene has Chekov trying on his everything was invented in Russia routine, and even though it finishes with a dramatic shift to red alert, that tension is rapidly deflated. Kirk quickly becomes the butt of the joke when they arrive at Space Station K-7, left on the backfoot in the conversation about the quad... the quadtri,.. the grain, constantly asking 'what, what', or 'so what?', and not being able to pronounce quadrotriticale, or even knowing what it is when Chekov of all people can cite chapter and verse. This of course cumulates in him being buried in Tribbles, and having to deal with various frustrations before he can even be dug out of the pile.
Kirk does get some good lines is as well, usually at Barris' expense (I'm very fond of "I was unaware that twelve Klingons constutues a swarm), which is fitting as the actual conflict of the episode is Kirk and Barris - he's the one who causes all the havoc and is the threat to Kirk. The Klingons are a complication here - Koloth has no link to Darvin's presence as best as I can tell, but the main reason that Darvin even poisoned the grain is so Kirk can uncover him and save the day.
Of course, the plot is in service of the comedy, and outside of Kirk's travails we've got some great wit between Spock and McCoy/Kirk, McCoy and Uhura when he takes a Tribble for examination, and the bar sequence with Scotty and Chekov that winds up in a brawl. And the comedy stands up 49 years later. It's not sophisticated but that sort of broad comedy is timeless.
I do have to say, the CG for the remastered episode feels more out of place than it did in Balance of Terror, with some panning shots of the Enterprise turning that felt quite clunky, and the insignia on Space Station K-7 really looked out of place for some reason. It looked more like CG fan art, or maybe the Ships of the Line calendar they do each year. and I feel like they missed an opportunity for an in-joke by not CGing any of the DS9 cast into the background. Indeed, they didn't use any of the CG establishing shots from Trials and Tribble-ations, even though they looked better IMO.