Revealing mistake: UFO - Timelash - in this episode the aliens with the help of 'turncoat' Turner have frozen a moment in time in which they will attack and destroy SHADO HQ. Everything and everyone is frozen in place - except for the guy in the background walking across the road during Straker's and Turner's 'car' chase in the 'Harlington/Straker' go carts.
Revealing mistake: "Computer Affair": In the interior shots of Mobile 1's cockpit, we see that there's a crew of 3 and that the pilot is black. But in shots of the exterior (miniature model stock footage), there's only one occupant, a pilot, and it's a doll with distinctively Caucasian features.
Revealing mistake: "Exposed": Another piece of stock footage used throughout the series was a shot of the shiny metal sign for Harlington-Straker Studios. The clock on the side of a building is reflected in the sign's surface, always showing the same time of day - so it's 1:50 every time Straker drives by.