Mulder says "rattlesnakes tend to hibernate in winter", however, reptiles (ectothermic animals, known commonly as cold-blooded animals) don't hibernate (just endothermic animals could have it, above all mammals). This process is called "brumation" for ectothermic animals.
Reverend O'Conner referring to the last book of the Bible as "the book of Revelations" is not a mistake. Not every religion or every translation of the Bible use the same title for this book. The commonly used and recognized titles are: The Book of Revelation(s), Apocalypse of John, Revelation to John or Revelation from Jesus Christ. For example the King James Bible and the The New Revised Standard Edition both call it "The Book of Revelation", the Gideon Bible calls it "The Revelation of Saint John the Divine" and The New World Translation calls it "A Revelation to John".
When Mulder and Scully first arrive at "The Church Of God" you can briefly see a crew member to the left of the screen as the agents are walking up the stairs.
There are no eucalyptus trees in Tennessee.
Reverend O'Connor pronounces the name of the last book of the Bible as "Revelations." The correct name is "The Book of Revelation to John." It isn't pluralized.