Plot hole: Hippolyta tells Hawkgirl of Aresia's background of being born in the outside world, the war in her country and right up to her drifting to the shores of Themyscira. It would be impossible for her to know anything of Aresia's background as in part two, it's explained that the captain of the ship who saved Aresia died shortly after reaching Themyscira and therefore would not have been able to tell Hippolyta anything.
Character mistake: Previous episodes have established this story arc to be occurring in the year 2154. Yet here, when T'Pol records her log, she cites the date as 2152. (00:32:00)
Factual error: In the episode where Sydney is supposed to be in Helsinki, there are visible skyscrapers in the background. There are no skyscrapers in Helsinki.
Factual error: In this episode we see Blithe get shot in the neck and are told that he died in 1948. In reality he was shot in the shoulder and survived. He later served in Korea and was promoted to master sergeant as well as receiving the paratrooper of the year award. Blithe died in 1967 while on active duty in Germany.
Factual error: Aetius' troops don't look anything like 5th century Roman soldiers. They are carrying a large rectangular shield, a pilum (a spear which was used for throwing) and a sword (gladius) on their right. This was typical for the Roman army until about the 3rd century A.D. In Aetius' time, the soldiers would have had smaller oval shields, a hasta (a lance used for stabbing and for fending off cavalry attacks) and a sword (spatha) on their left. Also, there would be an enormous amount of "barbarian" mercenaries in the Roman army (Goths, Vandals, even Huns.), so it was hardly a Roman army anymore. And where's Aetius' cavalry?
II (The Samurai called Jack) - S1-E2
Revealing mistake: When Jack cuts the flying car's hood off, he slashes it vertically, but it is cut horizontally.
Revealing mistake: When Shalimar is getting ready to leap on Gabriel, there is a quick glimpse of support wires attached to her.
Other mistake: Two Tiffs can be seen for a few seconds when King Dedede and Escargoon drive in.
Other mistake: In this episode, Eric tries to destroy a mutant, apparently unaware that Rangers don't destroy mutants but freeze them. Yet in Quantum Quest and Clash for Control, he froze a mutant.