Revealing mistake: As the gang drives up to the space-ship diner, cars are whizzing by in the background. When they are driving to the base there's also a clip of a fire truck going down the highway in the distance.
Revealing mistake: When Brad wears the sunglasses and holds the pole, you can easily see the string that holding it up.
Revealing mistake: At the river to cross over to Mt Weather, the vine used to swing across the river is just a standard rope, camouflaged. You can see it best when Finn recovers it after Jasper has jumped.
Unreal City - S2-E1
Revealing mistake: When Chandler and the others make it to the building where the bodies are being burned, the actor playing a corpse flips his hand over to hold onto the conveyor belt as he goes over the edge. (00:16:05)
Revealing mistake: When Bolivar's assistant comes running out of the theater where she found him, there are New York cabs as well as Toronto cabs in the background. The passing ambulances are marked as from Toronto, not New York.