The famous echoing chord from the theme music was a fluke. Composer Mark Snow accidentally rested his elbow on his keyboard with the echo function on and he liked the resulting sound so much, he wrote the theme around it. See more

Goofs

In many episodes it is clear that the agents are not in the region of the country or the world, described in the captions or the script. This especially becomes evident when the series began filming in Southern California and the vegetation and the terrain clearly could have only been that region. See more