As they enter the cave in 1519 one of the Spanish solders lights a torch, with a 20th century lighter. Even matches were not invented until 1827.
As Nero's sword is rising from the chest, the wires are extremely obvious.
Despite the fact she's just witnessed substantial paranormal effects due to Nero's ghost, Anne seems oddly skeptical about the idea of witnessing a miracle in this episode's tag leading into "The Walls of Jericho."
Several times during the Project HQ sequences there is an entirely immobile guard in the background (visible when Dr. Swain moves to the console), standing right next to the door to the outside. This appears to be a statue of some sort, as he never moves or shifts in position across multiple shots spanning a minute or two.
Phillip Ahn is Korean, but portrays the Japanese father of Lt. Nakamura (Mako, who is Japanese). Itsugi, supposedly a veteran Japanese soldier, is played by the Chinese actor Kam Tong.
When Doug breaks in to the storeroom he throws the crowbar he uses to open the padlock to the floor. The next shot is from inside the storeroom and when Doug walks in, he puts the crowbar on a crate.
This is a rare episode where the Time Tunnel pulls Tony and Doug out while they're still in their period clothing. There's no edit where they switch to their regular clothes, but of course, they use the stock footage of the opening time travel sequence, and sure enough they're back in their regular clothes for the next episode. At this point in the series, these clothes should have significant wear and tear with all the scuffles the guys have been in. Add the fact they should have a good amount of grime and major body odor. After all, at no time in the series had we seen Doug and Tony bathe and groom themselves. How is it that they begin every adventure immaculate and clean-shaven? No matter how long they've been stranded in one particular period of time, not even their facial hair grows! (editor's note: while this is somewhat of a recurring issue, it's not really a nit since the show itself is consistent on this - perhaps the two revert mentally and physically back to how they were when they first left - they certainly don't seem to reference anything that happened to them in previous episodes.)
On Major Hoffmann's office wall, there's a picture of Rudolf Hess, Hitler's deputy up to 1941. After Hess flew to Scotland year on an abortive peace mission that was unauthorised by Hitler, he was denounced and became reviled by the Nazi regime, so it's highly unlikely that an SS commander would have Hess' photo on his office wall in 1944, when this story takes place.
When Doug is being brainwashed to have his identity changed, he is shown slides of himself obviously wide awake, lucid and dressed in a Nazi uniform. How could such pictures already exist, given that Doug was taken off for brainwashing soon after being captured and did not don the Nazi uniform until after the brainwashing was complete?
When Mirabeau gets out of the car to help Tony get a wounded Doug into the car, you can see actor Robert Carricart slip and slide off-camera to the right. In the next shot he is well to the right of the two as he helps them up.
While the Time Tunnel scientists instruct David to jam the bomb's dial with one of the tools, all subsequent shots of the bomb upon returning to 1861 show the screwdriver David used merely sticking out of the side of the bomb, quite far away from the dial.
The tools that Kirk threw to David in the Time Tunnel should have been sent back to the depot with him and bomb (as they were also in the tunnel), but only the screwdriver David used to disable the bomb was shown as David reappeared in his own time.
From watching this episode, it appears that you could count the total population of the city of Baltimore in 1861 on your fingers. No-one is seen in the city streets apart from the plotter brothers, the Pinkerton men and Doug & Tony.
The layout of the bomb, the depot, and the train (and how Tony throws the bomb away) doesn't seem to make much sense. The bomb appears to have landed on the other side of the train from the depot, but there is no indication Tony threw it that far, or past the train earlier.
When the (stock footage of the) train pulls out, there is no sign of the depot or any buildings whatsoever.
The Pinkerton men fail to see the rather extensive brawl that Doug and Jeremiah have pretty close to the train as it departs near the end of the episode.
When Jeremiah and Matthew talk outside the depot about two-thirds through the episode, the voice sync on actor Scott Marlowe is not very well done. Particularly when he says, "No, no, no", his lips don't move at all, or fail to synchronize very closely with the on-screen dialogue.
Although the hints that the Time Tunnel has "forged its own connection" are intriguing, there's no real explanation for why the Project staff witness Lincoln's assassination in '61 at the beginning of the episode.
During the scene with Simon and a guard, Tony bumps into a streetlight which wobbles ominously.
When the prisoner returns to the island via the time tunnel, he lands on his feet, which is odd considering that even "experienced" travellers like Tony and Doug always end up rolling on the floor when they arrive.