Summary
- Doctor Bashir had multiple villainous moments in Star Trek: Deep Space Nine, starting with being possessed by Rao Vantika and committing violent acts.
- Alexander Siddig initially felt unprepared for the evil version of Bashir/Vantika, as he didn't have enough time to prepare for the role.
- In a later season, it was revealed that Bashir was replaced by a Changeling, who framed another character to keep the crew distracted.
Doctor Julian Bashir (Alexander Siddig) has been a villain in Star Trek: Deep Space Nine on five separate occasions, though he wasn't always aware of his actions. Beginning life as an arrogant young medic and persistent but unsuccessful suitor for Lt. Jadzia Dax (Terry Farrell), Julian became a complex and fascinating member of the DS9 ensemble. Julian's love of spy stories, his dark links to the legacy of Khan Noonien-Singh (Ricardo Montalban), and his friendship with Elim Garak (Andrew Robinson) gave Bashir some of his best Star Trek stories.
Star Trek: Deep Space Nine season 5 became a watershed moment for Bashir as revelations about his genetic enhancements, and suspicion about his involvement with the Dominion completely changed the course of his character. In the latter seasons, Star Trek: Deep Space Nine's Doctor Bashir revealed his dark side as he took extreme measures to extract information from Section 31's Luther Sloan (William Sadler). In writing these darker storylines, the DS9 writers' room were likely inspired by Alexander Siddig's previous portrayals of Doctor Bashir's more villainous side.
5 Rao Vantika Takes Over Doctor Bashir's Body 
In Star Trek: Deep Space Nine season 1, episode 9, "The Passenger", Doctor Bashir attempts to save the lives of a Kobliad criminal called Rao Vantika (James Harper). Vantika has an extensive list of horrific crimes, driven by his desire to cheat death. As a result, Vantika's nemesis, the law enforcement officer Ty Kajada (Caitlin Brown) refuses to believe that the criminal is finally dead. It's revealed that her suspicions are correct, as Vantika was able to transfer his mind into the body of Doctor Bashir seconds before he died. While inhabiting the body of Bashir, Vantika violently attacks Quark (Armin Shimerman), tries to kill Kajada, and authorizes the deaths of a freighter crew transporting a valuable shipment of deuridium.
Alexander Siddig later reflected that his work on the "evil" Doctor Bashir episode was one of his biggest failures. In an interview with Star Trek Communicator, Siddig said that he hadn't been given enough time to prepare to play this more villainous version of Bashir/Vantika. The delay to his receipt of the script was likely caused by the decision to remove Ty Kajada as the new host of Vantika's consciousness. So unprepared was Alexander Siddig for the role of Vantika that he later re-recorded his dialog to be dubbed over the existing footage as the previous voice was – according to Rick Berman – too much like horror legend Bela Lugosi.
4 Bashir Is Replaced By A Changeling On The USS Defiant 
In Star Trek: Deep Space Nine's season 3 finale, a Changeling infiltrates the USS Defiant in an attempt to trigger a war between the Federation and the Tzenkethi. In a Star Trek take on the classic sci-fi movie The Thing, the crew of the Defiant deal with paranoia as they try to root out the infiltrator. Doctor Bashir was replaced by a Changeling, so that they could take control of the blood screening to identify the impostor. The Changeling Bashir framed Lt. Commander Michael Eddington (Kenneth Marshall) in the hope of keeping the crew busy until their plan could be completed.
In writing "The Adversary", it was decided that Eddington's enigmatic nature would make him the perfect red herring. That means that while Alexander Siddig is playing a villainous Bashir, the audience is focused on Eddington and whether he's a Changeling. So successful was Marshall's portrayal that fans still suspected that Eddington was a Changeling infiltrator, even after Constable Odo (Rene Auberjonois) killed the real Changeling impersonator. This convinced the writing team to go in a different direction for their next big Changeling infiltrator, by returning to Doctor Bashir.
