Quark (Armin Shimerman) and his fellow Ferengi were just as close when off-set from Star Trek: Deep Space Nine as on it. Although the Ferengi were introduced in Star Trek: The Next Generation, they really came into their own during DS9. The Ferengi were an ideal fit for the more mature direction that DS9 took the franchise in, with their loose morals and thirst for profit brilliantly fitting into the more complex morality of the show.
At the core of DS9's Ferengi stories was a family - Quark, his brother Rom (Max Grodénchik), and Rom's son Nog (Aron Eisenberg). Each of them had a proper narrative arc that added motivations beyond simple profit. This sort of depth that hadn't been seen in Star Trek: TNG's Ferengi characters up until that point. Quark, Rom, and Nog were, therefore, an integral part of the DS9 cast, and their familial ties were reflected in their off-set relationships.
Quark, Rom And Nog Were A Real-Life Ferengi Family
Discussing the making of DS9 in the retrospective documentary What We Left Behind, Armin Shimerman reveals that he and Rom actor Max Grodénchik unknowingly developed their brotherly relationship through rehearsals at Shimerman's house. So successful were these rehearsals that DS9 showrunner Ira Steven Behr was convinced the Ferengi would work based on the chemistry between Quark and Nog. These rehearsals eventually extended to the expanding cast of DS9's Ferengi characters, especially when it came to the Ferengi-centric episodes.
The camaraderie forged in these rehearsals at the home of DS9's lead Ferengi, Quark aided the actors on set, who were a close-knit team. In an interview about his time on DS9 Shimerman said [via Comicbook.com] "the Ferengi were all encased in a great deal of prosthetic rubber, and we knew that our days were long, and we knew that if we didn't drink enough water, or if we overdid, we would be wiped out long before the other actors". This meant that the Ferengi actors looked out for each other, like a family, and these rehearsals meant they could build those relationships to better benefit the scenes and episodes they shared.
DS9's Ferengi Episodes Were Some Of Its Best
The chemistry between Shimerman, Grodénchik, and Eisenberg was key to what made DS9's Ferengi episodes so great. Episodes like "Little Green Men" and "The Magnificent Ferengi" have gone down as some of the most memorable episodes of the show. This is partly due to how the comedy of these Ferengi episodes defused the dramatic tensions of DS9's Dominion War. Telling stock Star Trek stories from a profit driven Ferengi perspective also allowed writers to flip Gene Roddenberry's egalitarian morals on their head. For example, Quark isn't bound by the Prime Directive, so is delighted by the prospect of making money from the more primitive humans in 1940s America in "Little Green Men".
The closeness between DS9's Ferengi actors also provided a great deal of pathos alongside the comedy. In "It's Only A Paper Moon", Nog deals with post-traumatic stress disorder in a nuanced and emotional character piece that adds real dimension to the character beyond the snarling caricatures first introduced in TNG. No Star Trek show since has done anything nearly as interesting with the Ferengi as Star Trek: Deep Space Nine, and with Shimerman having recently returned to the role, it's hoped that the character could get a bigger focus in the future.