Revealing mistake: At the apartment complex fire, after Johnny is knocked unconscious by the explosion, when the Pasadena fireman finds him and has to lift him up, it's funny how even though Johnny's unconscious we can see that he actually helps to stand himself up, so the fireman can lift him up and carry him out.
Revealing mistake: After Rygel realizes that he can loosen the soil with the dumped gruel, it cuts to John and Aeryn as they approach the Tavlek camp, and when Aeryn tells John, "I am going to take out every last Tavlek. No survivors. No mercy. Now give me the oculars," John holds up the syringe (with Zhaan's sleep mist) that Aeryn had given him earlier, and we can see "DG-4" engraved on the side of the gun, revealing that the prop dept used the model DG-4 aluminum air blow dust gun to play the part of the syringe.
Revealing mistake: (Part 4) After Omega takes off his mask and looks in the mirror, when he sees that his physical body doesn't exist he puts his mask back on and screams, but when he shouts, "If I exist only by my will, then my will is to destroy," Omega's mask pops up off his face, and we can see the actor's blackened face as he shouts the last bit of his dialogue. (00:07:10)
Revealing mistake: There are numerous times throughout the series where the supposed big city of Metropolis is actually just a back lot set and none of the buildings are more than a couple of storeys high. Quite often the green hills of Southern California can be seen beyond the set and between the buildings.
Revealing mistake: When they show the soldiers killed by the Dalek, in both the hallway outside the cage and the large room in weapons testing, they show some casings which were ejected from the soldiers' guns. The casings still have projectiles in them. If used, they would have been in magazines and would never fall out like they are shown.
Revealing mistake: With Marshal Mars in pursuit, as Ray drives his pickup, he holds the steering wheel with his left hand, and his stiff prosthetic right arm is down at his side. When Kate grabs for the steering wheel, in the side exterior shot the stunt driver is quite noticeable, as he grips and turns the steering wheel with his good right hand/arm. (00:30:40)
Revealing mistake: In the first shot of the scene where Emma and the others arrive in Storybrooke in their cars, on the left side of the screen, you can see a sign behind a branch. It says "Steveston Museum and Visitor Centre." Steveston is the name of Canadian town which doubles as the town of Storybrooke on Once Upon a Time. (00:07:00)