Knight Rider [Pilot; a.k.a. Knight of the Phoenix] (1) - S1-E1
Revealing mistake: When KITT takes part in the race and goes up on two wheels, you can see that the stunt driver is behind the wheel and that a dummy is strapped into the passenger's seat.
Revealing mistake: When Frasier comes into the chalet after skiing he doesn't show any of the visible effects after a hard day on the slopes. Meaning, his face isn't even flushed from the cold, his hair is perfectly combed after wearing a hat and there is not even a drop of snow on his boots.
Revealing mistake: When Jerzei is coming through the door with an axe, you can see the door is paper thin to make it easier to get through. In fact you can see Alexei Sayle being very careful to only chip small bits away because a decent whack with the axe would smash the whole thing down.
Revealing mistake: When the coward is being branded using a red hot poker, you can see that the metal 'C' hasn't been heated at all when it is brought next to his face. Compare it to when they tested it on a piece of wood beforehand. The poker is also covered in a really fake-looking red paint. (02:02:55)