The X-Files premiered on American television in 1993 and followed FBI agents Fox Mulder and Dana Scully as they investigated paranormal cases, with Mark Snow composing its distinctive theme. The whistling melody became closely tied to the show's mix of science fiction, mystery and conspiracy, and it has lived on in parodies, reaction videos and memes long after the original run. Creators still use it as instant shorthand for the unexplained, because almost everyone recognises the tune within the first few notes.