I was without a television and VCR for about eight years, and so I hadn’t been able to watch my Star Trek: TNG and DS9 tapes in quite a while. Having recently acquired a new TV and VCR, I’ve been enjoying watching all of these episodes, one after another. I’ve discovered that watching them all so close together allows me to notice things that I probably wouldn’t notice while just watching the episodes ones a week as they were aired. So perhaps some of you can help me out with a few “issues” I’ve discovered (apologies for not having episode titles at hand):
1 - In The Next Generation, we saw that the big-eared Ferengi don’t like loud noises. Specifically, in the Ferengi’s first appearance, while on the alien planet with members of the Enterprise crew, the Ferengi would scream and writhe in agony at every clap of thunder. Understandable. But flash forward a few years to the DS9 episode where Quark and Rom travel to the Ferengi homeworld to deal with their mother’s misbehavior. we see that the weather on Ferengar seems to consist of constant rain and thunderstorms! So why do Ferengi, raised on a thunder-prone world, hate thunder on an alien planet?
2 - In the TNG episode, “The Host”, the Trill race is introduced. The Trill, Odan, makes it quite clear that he will not travel via transporter because doing so would damage his symbiont. And yet, in DS9, we see Jadzia Dax cheerfully transporting on a regular basis. With no mention of any ill effects to the symbiont. What’s up with that?
3 - Data. Somewhere around the fourth or fifth season, Data mentions that he has been in Starfleet for twenty-six years. A major character point was that Data desperately wanted to become human. In the first season, we saw an android severely lacking in human characteristics. He became more and more human as the TNG series progressed. So why did he make such dramatic progress in the seven years of TNG, but almost no progress in his previous 18 - 20 years in Starfleet?
4 - Generic alien ships. There have been numerous alien races that have appeared in only one episode of TNG. In many cases, we were shown the ship used by that race, and this is the best example of what I meant by noticing things when watching episodes back-to-back rather than once a week. These one-shot aliens all seem to use the same ship! The ship I’m talking about is always brown/bronze in color, and kind of wedge-shaped, with a blunt nose. It’s dramatically smaller than the Enterprise. Watching the show when it was originally aired, this ship was probably seen only 3-4 times per season, with the instances being spaced out over the course of the season. So you wouldn’t really notice the repetition. But I watched the entire series over the course of about two months, so naturally I noticed the same ship showing up over and over. I have also seen this same ship design docked at DS9 several times. This leads me to the conclusion that this is simply a “standard design”, perhaps built by some commercial interest, and sold to any interested buyer. Kind of like a Boeing 747 - built in the USA but sold to airlines around the world. So this starship is purchased by many different races, and then perhaps converted by the buyers to different configurations for different purposes. I’m also starting to get the impression that this is a Vulcan ship. Do the Vulcans build and sell ships to other planets? Or perhaps provide other races with the design for this ship?
Thanks for any information on these questions 
Notice they altered more than Ferengi couldn’t handle loud noises in the episode the Ferengi were first introduced. It’s like there was a major shift in the way Ferengi behaved in just a few years.