Revealing mistake: When Queen Elizabeth arrives in disguise, Blackadder welcomes her and is about to open the door to the closet, but you can see the door is being pushed up from the inside, probably by a crew member. (00:16:50)
Revealing mistake: When Dori types in an inquiry into the computer it is very obvious that her typing is absolutely nonsense - she types the same three letters in a row over and over again, and never presses Enter. (00:19:05)
Revealing mistake: The extras and actors are made to appear to be naked as they live in a nudist colony, but many of them are wearing some kind of undergarment.
Monster in the Playhouse - S1-E9
Revealing mistake: As Reba the Mail Person exits the Playhouse, she goes past the window, and you can see her exit the sound stage through a door painted the same as the background.