Knever

Mirror, Mirror - S5-E11

Revealing mistake: When Carter and Jo almost crash into the reflective smart dust wall on the road, Carter puts his hand up and waves it, to see his mirror image doing the same. Carter's mirror's hand movements are out of sync, which reveals that the "mirrors" are the actors, and the "real people" are doubles.

Knever

Liftoff - S4-E11

Revealing mistake: When Jo comes riding in with the horses, you can tell that it's a stuntwoman in the far shot.

Knever

All the Rage - S4-E3

Revealing mistake: In the very first shot, we see the sky, and you can tell it's a digital image imposed on a green screen instead of a shot of the actual sky.

Knever

Primal - S1-E9

Revealing mistake: When we first see the army of Starks outside Global Dynamics, it's quite obvious that only one of them is actually the actor that plays Stark; the others are merely people who look similar.

Knever