Between the fate of the Odyssey (one of the rare times we saw a Galaxy-class starship destroyed in battle), the duplicitous nature of the Vorta and the Dominion in general, Season 2 ends with signs of trouble coming.
Quark gave Sisko some examples of things he can sell using the DS9's monitors, which included Vulcan IDIC pins. I wonder if that is an in-joke/reference to IDIC which was created by Roddenberry in TOS, at least partially as a marketing tool to sell IDIC pendants/pins.
Jake said that if Nog doesn't get a good grade on his science project, he would drop out of school.
I didn't realize that this was one of the key points in Nog's development arc. If it wasn't for Jake offering and Sisko agreeing to take Nog along, he may not have gone to the Academy.
When someone says "it will just be like a vacation" at the start of a story, you know it won't be a vacation. It's like saying "what can possibly go wrong?"😉