Science Fiction shows are mostly shot in Vancouver, so it’s unavoidable that sometimes they will share locations.
But due to the magic of video editing, set designs, camera angles, and lighting most of the time shared sets go unnoticed. However, fans quickly pointed out that the latest episodes of Supernatural and The X-files use the same abandoned ship location.
What’s even more shared are the plot devices used in both episodes. Namely Wayward Sisters and Ghouli. Those are the last two episodes of both shows that I’ve watched. In them we have the following pairings, Sam/Scully, Dean/Mulder, Ghouli/whatever the heck those creatures from the bad place are called.
Both episodes also feature portals although, Supernatural’s make way more sense and has been an ongoing plot for many episodes. Sorry X-Files, Supernatural has always done Monster episodes way better.
It’s highly unlikely that the X-files and Supernatural share the same universe, but take away aliens, and X-files Monster of the week episodes, basically are Supernatural. So it may not be out of the realm of possibilities that Mulder could show up on Supernatural one day. After all, Supernatural is crossing over with Scooby Doo later this year.
Fun Fact: Fox Mulder does not exist in Coffee shops.