Starring: Leo G. Carroll, Stefanie Powers, Noel Harrison
The Garden of Evil Affair - S1-E8
Deliberate mistake: The bad guys chase Mark through a movie studio backlot past a London bus with a large red "Out of Service" sign on its side. During the ensuing shoot-out scene, the film is reversed for some reason, and the sign on the bus is suddenly backwards. (00:24:20)
The Prisoner of Zalamar Affair - S1-E2
Revealing mistake: Mark finds the bomb planted under his Jeep and puts it under the bad guy's car instead. When it explodes, there's a huge cloud of smoke, but before the shot cuts, you can see that the car is completely undamaged. (00:10:30)