Fox’s The X-Files is one of the most groundbreaking sci-fi drama series of all time. Although it was initially considered a cult series back in the 90s, over time, Chris Carter’s creation has become a highly-regarded fixture of pop culture. The X-Files was so successful that the original series ran from 1993 to 2002 with nine seasons and over 200 episodes, then, had a revival that lasted from 2016 to 2018. In addition to this, the franchise also counts with two films.

Although on screen Mulder and Scully’s had great chemistry and a good-natured companionship, in real life The X-Files costars had a rather complicated relationship, to say the least. It’s no secret that throughout the show's run, David Duchovny and Gillian Anderson had an ongoing feud. Turns out, their relationship was so strained that Duchovny and Anderson would go as far as cutting all communication off-screen with each other while shooting The X-Files.

Related: Was Gillian Anderson Underpaid For 'The X-Files'?

The X-Files Became A Highly Successful Franchise

Created by Chris Carter, The X-Files is a science fiction slash thriller television series that first aired in September 1993. The plot revolves around two FBI special agents, Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson), who investigate numerous unsolved cases involving paranormal activity. Slowly, the series gained tons of popularity.

Both the show and the lead actors, Duchovny and Anderson, were highly praised and received multiple awards and nomination. By the time The X-Files came to an end, it had become one of the longest-running science fiction series in the history of U.S. television. With all this success, it’s no wonder the creator decided to create two spin-offs, The Lone Gunmen and Millenium, two films, books and even a videogame in an attempt to expand The X-Files franchise.

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By the early 2000s, the franchise had generated more than a billion dollars in total revenue, with $500 million coming from the original series alone. This explains why they decided to create the messy revival of The X-Files that premiered in 2016, but came to and end after only two seasons.

Gillian Anderson and David Duchovny’s Off-Screen Relationship Was Very Different From What Fans Saw On The X-Files

It’s no secret that, despite working together for so long, Gillian Anderson and David Duchovny didn’t get along. While their characters shared a good-natured camaraderie, that would later evolve to a romantic relationship at the end of the show, the two actors would rather keep their distance behind the scenes. The biggest mystery surrounding The X-Files has to be the reason behind Anderson and Duchovny’s life-long feud.

Related: Inside David Duchovny's Complicated Relationship With 'X-Files' Co-Star Gillian Anderson

The reason behind Anderson’s and Duchovny’s complicated relationship has never been cleared. Some claim that it began because they were obliged to work together for long periods of time when filming The X-Files and, eventually, their personalities ended up clashing. Others point out the salary disparity between the two costars during the early stages of the show as the main reason for Anderson’s dislike for David Duchovny. But the real reason has never been disclosed by the actors.

Anderson Revealed That Her Relationship With Duchovny Was So Bad They Wouldn’t Talk While Filming The X-Files

Both actors have openly talked about their not-so-good relationship on countless occasions. Back in 2008, Duchovny talked to Metro about the open hostility both had towards one another while filming. "Familiarity breeds contempt. It’s nothing to do with the other person. All that fades away, and you’re just left with the appreciation and love for the people you’ve worked with for so long. We used to argue about nothing. We couldn’t stand the sight of each other.", he explained.

And in 2015, Anderson revealed to The Guardian that working alongside Duchovny for so long was hard. “I mean, yes, there were definitely periods when we hated each other.”, she admitted. “Hate is too strong a word. We didn’t talk for long periods of time. It was intense, and we were both pains in the arse for the other at various times.”

Nowadays, it seems like Anderson and Duchonvy’s relationship has improved. In a 2016 interview with Jimmy Kimmel, both actors even joked about their so-called feud during the filming of The X-Files.