Revealing mistake: When Freeth, Carter and Regan raid the flat, Freeth breaks the door down - the door starts to fall before Freeth hits it.
Revealing mistake: Not only is the stunt double's face visible in several shots during the apartment fight scene, the man is also noticeably taller and heavier than Robert Wagner, and is wearing a really bad wig.
Alpha Child - S1-E7
Revealing mistake: As the alien ship approaches Alpha on screen, there is a round, blank area where the model moves, and as the vessel nears the camera, the edge of the cell used for the picture of the vessel is visible.