When Worf and Jadzia first meet he says to her that Curzon Dax was an honored name among his people, and she replies to him in Klingon. When asked what she said by Kira she replies "it loses something in translation". What she said was: "Yeah, but I'm a lot better looking than he was."
This was the third time a large-scale change was made to the opening credits of a Star Trek series (other than changes to cast credits). The first was during Star Trek (1966), when they changed the theme song to include a singer. The second was during Star Trek: The Next Generation (1987) when they moved the opening sequence from Earth's solar system to new, previously unseen planets. The third was in the beginning of season 4 of Deep Space Nine when they added ships coming and going from the station to make the station seem more "active" as well as a faster paced, more "heroic" version of the theme song.
Takes place after the events in Star Trek: Generations (1994). Sisko references the crash landing of the Enterprise at the end of the movie.
When Odo stops Drex from harassing Morn he insults Odo in Klingon, what he said was: "Does your mother let you talk to adult men?"