Trials and tribble-ations

I'm going on with "Star Trek", and I always try to find links with the original serie. And this time the link is very strong.
This month we have a "Deep Space 9" episode, the only Star Trek serie where we don't find the usual spaceship heading for the unknown.
As I have already explained in the dedicated page, "Deep Space 9" takes place on a space station with a diplomatic mission, orbiting around a planet where a long war has just ended. The situation is very similar to "Babylon 5", which a large number of viewers think it has been copied by "DS9" and the elements for prosecution can be easily found...
This is an unusuale episode anyway, the leading characters have just accomplished a mission and are aboard the "Defiant", a little ship which can't be compared to any "Enterprise" version.
But the episode is really interesting because it takes place... during an original serie episode, the famous "The trouble with tribbles".
Better to recall the story: on the K-7 space station (in a certain way an ancient version of DS9) a load of grain has been stored, and it will be used to colonize a planet claimed both by the Federation and the Klingons. The grain would help the Federation, so Captain Kirk's Enterprise is ordered to escort the station.
The Klingons arrive soon, of course, and there is risk of enemy spies on the station. In this complicate situation, where Kirk can't get rid of an eager Federation executive, another confusing element appears: the tribbles, strange little animals similar to furry balls. But they have a big problem: they are born pregnant, and if they are well fed they can reproduce every 12 hours... in a three days time the Enterprise and the K-7 are invaded by the furry balls, which have grown to 1,771,561, following Spock's calculations... and have eaten part of the grain.
Baris, the Federation executive, is very angry, and menaces the end for Kirk's career, but tribbles prove to be useful: almost all of them are dead, because the grain has been poisoned. Their hate (returned) for Klingons gives to Kirk the chance to expose the spy: Arne Darvin, Baris 'assistant, a disguised Klingon.
To clean uo the Enterprise, Scotty has the right idea and beams all of them aboard the Klingon ship...
In this DS9 episode Captain Sisko meets an aged Darvin who manages to go back in time to kill Kirk before the young himself is exposed. Sisko and his men have to wear the Enterprise uniforms and beam aboard the ship and the station to find Darvin and prevent him from altering history.
The episode is really intriguing, and alternates new shots with Captain Sisko and the others with the classic ones with Captain Kirk: moreover, like famous movies like "Zelig" or "Forrest Gump", we see the DS9 crew meeting the Enterprise men... a real masterpiece.
Cleverly, the actor who portrayed Darvin in the original serie, Charlie Brill, is back again for the same role (and he is correctly aged).
Just a negative note: the mean used for time travel isn't a very brilliant idea, an "orb od time" makes us think to fantasy stories, Star Trek's scientific exactness seems to have been forgotten.
There's another strange blooper: Captain Kirk's Enterprise is said to be the very first one. "Star Trek - Enterprise" hadn't come yet, unless we are counting only the Federation ships...
There's also the problem of feature difference between the original serie's Klingons and the following ones: Worf refuses to explain all the true story, the real thing is that when the first Star Trek motion picture was shot they wanted to improve the Klingon features without thinking about the previous ones and, surely, without foreseeing the following four Star Trek series and the need for an explanation...
Enjoy.