In a Mirror, Darkly (1) - S4-E18
Trivia: In the opening scene of this episode (S4E18), footage from the 1996 movie "Star Trek: First Contact" was ingeniously intercut with new footage to create a startling revision that is still a Star Trek fan favorite to this day. Actors James Cromwell (Zefram Cochrane) and Cully Fredricksen (the Vulcan emissary) shot the original scene for the film "First Contact" in 1995. When the TV series "Star Trek: Enterprise" recycled the movie footage 10 years later, both Cromwell and Fredricksen received a day's pay for appearing as extras in this TV episode (about $120 for a day's work in 2005), even though they never physically appeared on the "Enterprise" set.