Star Trek: 10 Things You Didn’t Know About Quark
8. He changed over time
At the start of Star Trek: Deep Space Nine and throughout its first few seasons, you could argue that Quark was like any other Ferengi, strictly adhering to The Rules of Acquisition and putting his own profit ahead of everything else.
But as the show went on, his constant scheming and swindling became less and less frequent, or at least the nature of it had changed. In the early seasons, he cared more about latinum than his own brother, but later on he would show his softer side.
This was most noticeable during the Dominion War storylines, especially when the Dominion forces were in control of Deep Space Nine. For example, he risked his own safety to obtain secret information from Damar in the season six episode Behind the Lines; and in season seven's Shadows and Symbols, he accompanied Worf on what was basically a suicide mission to the Dominion shipyards just to ensure that Jadzia could get into Sto-vo-kor.
That sort of unselfishness and willingness to sacrifice are not the hallmarks of a Ferengi, and even Quark himself wouldn't think of doing such things just a few years earlier. This just shows how committed the writers of Deep Space Nine were to letting their characters grow and evolve over time.