Revealing mistake: In episode 3x10, Remnants, when Lazare shows up to talk to Will, we see that his left hand has been cut off. When Lazare is about to leave, he has his hands at his sides, and we can see that both arms are the same length, but the left one should be shorter, because it has no hand.
Revealing mistake: At one point when Alan's phone rings (Nokia 8310) he answers it and talks to the caller yet it's obvious he isn't talking to anyone. He blatantly presses the red/cancel button to answer the call. The image hadn't been reversed though, because he pressed the exact same button to end the call.
Revealing mistake: When Captain Liberty writes The Terror's phone number on the napkin we can plainly see that she is using a blue bic ballpoint pen - but when we get to see the napkin she had written the number on (again - second napkin) it was written by a felt-tip marker.
Revealing mistake: While Archer and the crew discuss the capabilities of The Xindi vortex technology and whether or not to go to Azati Prime, Archer asks Trip to see the data that Trip has collected from the Degra's ship. The camera pans to the display screen, on which a Mac mouse pointer is visible. It is positioned on the line going downward from the red giant.
Revealing mistake: Paul Devildis calls the bank to discuss his restructuring plan. During the shots of the two bankers, on the desk is a notebook-sized, plain brown box. It is very distinctive as it is blank except for a single square white label on the front. Later in the episode Paul delivers his restructuring plan with the bomb inside to the bank. It is in this same box.