Garak is introduced in the second episode of the first season of Deep Space Nine "Past Prologue". In the episode, he appears in the replimat on Deep Space Nine, where he introduces himself simply as "Garak", a tailor exiled from Cardassia, to the station's doctor, Julian Bashir. In the same episode, it is discovered that Garak was simply known as "The Spy" to the crew of Deep Space Nine, being the only Cardassian left on the station after Cardassia withdrew their occupation from the nearby planet Bajor.
Over the course of the series, Garak at first denies involvement with the feared Cardassian intelligence agency the Obsidian Order, only to later reveal his connections as he (or as the plot) deems necessary. As Garak's friendship with Bashir develops, it is revealed that he was one of the Obsidian Order's highest ranking operatives, and that he was exiled from Cardassia for unspecified reasons. The details of Garak's exile are never revealed, but it is suggested that his exile resulted from either letting prisoners escape during the occupation of Bajor, or betrayal of Enabran Tain, the head of the Order, who is later discovered to also be Garak's resentful biological father. Garak's constant enigmatic secrecy keeps him a character of both interest and importance in the series, and he later uses his contacts with Cardassia and the training he received as an operative of the Obsidian Order to assist the Federation in the war against the Dominion.
Despite not being one of the main characters, Garak appears in 37 of the 176 episodes of Deep Space Nine, including the series finale, and appears in each of the seven seasons.
Upon his introduction in the series, Garak was intended to be a one-shot character, and not a character that was to be developed or even appear in the series beyond a single episode. Robinson stated that he portrayed the character in the episode for the simple fact that he needed money for that month to pay his bills. The producers were impressed with Robinson's performance as Garak, and decided to develop the character after Robinson agreed to return as the character for future episodes. The decision to incorporate Garak into more of the series actually resulted in Garak becoming a pivotal character—transforming him from a simple one-time character to one of importance and unusual complexity and resonance.
Robinson's initial performance as Garak received scrutiny as his portrayal was interpreted as Garak being homosexual or bisexual. Robinson denied that his portrayal was intended to portray Garak as homosexual, and, rather, implied that he was omnisexual. As a result of the controversy, Robinson removed the particular characteristic from Garak.