who played mulder in the x files?
David Duchovny
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 " Sleepless " marked the first on screen appearance of Steven Williams as Fox Mulder 's new source , " X. " The character was originally intended to be a woman , and an actress was cast in the role , but after shooting her first scene the role was recast with Williams , an actor who had previous experience with writers Glen Morgan and James Wong . Natalija Nogulich , the actor who originally earned the role , was replaced because the writing staff felt she was not able to create the " right chemistry " between her co @-@ stars . 

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 The show centers on FBI special agents Fox Mulder ( David Duchovny ) , Dana Scully ( Gillian Anderson ) and John Doggett ( Robert Patrick ) who work on cases linked to the paranormal , called X @-@ Files . In this episode , Mulder secretly conducts his own investigation after a man is gunned down on the White House lawn attempting to inform the President of a planned alien invasion . However , he is soon in over his head as he tries to expose further evidence of colonization . 

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 The first season introduced main characters of the series , including Fox Mulder and Dana Scully who were portrayed by David Duchovny and Gillian Anderson respectively , and recurring characters Deep Throat , Walter Skinner and Cigarette Smoking Man . The season introduced the series ' main concept , revolving around the investigation of paranormal or supernatural cases , known as X @-@ Files , by the Federal Bureau of Investigation ; it also began to lay the groundwork for the series ' overarching mythology . 

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 News of Mulder 's arrest spreads to the FBI . Upon hearing that he has resurfaced , and in such a dire manner , Dana Scully ( Gillian Anderson ) and Walter Skinner ( Mitch Pileggi ) visit him in military custody . During his time in captivity , Mulder receives mysterious visits from two phantoms of his past : Alex Krycek ( Nicholas Lea ) and X ( Steven Williams ) . Meanwhile , Scully and Skinner go to great lengths to get him released , but are unsuccessful . Mulder 's fate is ultimately made the subject of a military tribunal with Deputy Director Alvin Kersh ( James Pickens , Jr . ) in charge . At the outset , it appears Mulder will become the hopeless victim of a show trial stacked against him . 

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 Hoping to continue the series , Carter introduced a new central character to replace Mulder : John Doggett . More than 100 actors auditioned for the role , with only about ten considered by the producers . Lou Diamond Phillips and Hart Bochner were among the auditionees , and Phillips , Bochner and Bruce Campbell ( who played Wayne Weinsider in a previous episode of The X @-@ Files ) were considered for the role , but the producers eventually choose Robert Patrick . The season also introduced Monica Reyes ( portrayed by Annabeth Gish ) , who would become a main character in the following season . 
