Shared with you
The character of Morn (Mark Allen Shepherd), the Lurian bar patron who is always seen sitting at Quark's bar, was written as a nod to the character of Norm Peterson, played by George Wendt on Cheers (1982). Morn is an anagram of Norm. The mask worn by Shepherd originally had no opening for the mouth, so make-up artist Michael Westmore gave him lips over the course of the series, in case the character needed to speak. Several lines for Morn were scripted over the years, but unfortunately for Shepherd, these were always written out at the last moment. So Morn never said one word during the entire run of the show, leading to a running gag where bar patrons, station crew members and civilian residents often mention that Morn is excessively talkative off-screen, and "never shuts up."
Kira was a last-minute addition to the cast. The original plan was to include the Star Trek: The Next Generation (1987) character of Ro Laren, but Michelle Forbes didn't want to do a series at the time.
Although we only rarely see it, there is an ATM in Quark's bar. It dispenses the various types of currency used by major races visiting the station: Federation credits, Bajoran litas, Cardassian leks, and Ferengi latinum.
Colm Meaney was initially reluctant about signing onto the series. Meaney was comfortable playing O'Brien on an episode by episode basis for Star Trek: The Next Generation (1987), and at the time, was unsure if he wanted to play a full time television role.
Armin Shimerman (Quark) and Marc Alaimo (Gul Dukat the Cardassian) appeared as one of the first actors to portray members of their respective species, and both appeared on Star Trek: The Next Generation (1987). Shimerman played the Ferengi officer Letek in The Last Outpost (1987) while Alaimo played the Cardassian officer Gul Macet in The Wounded (1991).
Michael Dorn did not want to reprise his role as Worf, since the daily make-up application was exhausting, and he was relieved to be able to move on. Dorn said that the salary he was offered made him reconsider.