Revealing mistake: Whenever somebody closes a door, leans against a wall, or goes up/down the stairs and brushes against the wall, it wobbles, revealing that the walls are lightweight stand-up props.
Revealing mistake: When Manuel throws the grapefruit at the other guests, you can see the woman closest to the camera react before Manuel throws it. (00:11:00)
Revealing mistake: When Basil sends the grapefruit flying, we see Polly go through the doors to the kitchen. However, if you look closely at the doors as she goes through you will see just a plain wall. Not the kitchen as is seen in other episodes. (00:11:00)
The Builders - S1-E2
Revealing mistake: In the part where John Cleese is smacking Manuel's head against the place where the dining room doors are supposed to be, you can see very that Manuel is kicking the wall right when his head is supposed to hit it, creating the sound of his head hitting the wall. Check it out because it's very obvious and hard to miss. (00:16:05)
The Builders - S1-E2
Revealing mistake: When Basil smashes Manuel against the wall where the dining room is meant to be, we can see it is made out of cardboard. Notice how it begins to fall off, even though it is meant to be sealed and covered in wallpaper. (00:16:05)
Suggested correction: Perhaps this was due to O'Reilly's shoddy workmanship?
You could say that but Fawlty towers had wobbly sets all the time. I would say this would be covered under "mistakes".
Where is the 'codswallop' as you so euphemistically put it? To me it looks like O'Reilly cut corners by shoddily placing a sheet of plasterboard in the doorway without attaching it well then shoddily wallpapering over it. Hence the reason for it falling out.
The Builders - S1-E2
Revealing mistake: Look at the skirting board of the section of wall Basil hits Manuel against. There are black shoe marks on the paint from previous takes where Manuel kicks the board. (00:16:15)
The Builders - S1-E2
Revealing mistake: The umbrella Sybil uses to hit O'Reilly and Basil with is padded to protect the actors. (00:23:30)
The Builders - S1-E2
Revealing mistake: In the scene where Polly brings Mr O'Reilly a cup of tea, it is obvious on several occasions that there is nothing at all in the cup. Not only does he hold it in such a way that you can see inside, but when Basil snatches it away nothing spills out.
The Wedding Party (a.k.a. Sex) - S1-E3
Revealing mistake: Basil goes back to the second floor chasing after Polly. As he passes the last part of the banister, he touches the edge of it and it wobbles like rubber. (00:24:00)
Gourmet Night (a.k.a. Gourmet's Paradise) - S1-E5
Revealing mistake: When the Colonel first meets Basil, the same shot is used twice of the Colonel twitching.
Gourmet Night (a.k.a. Gourmet's Paradise) - S1-E5
Revealing mistake: When Basil is out of the car and shouting at it after its final breakdown, you can see a crew member reflected in the right hand side of the windscreen giving John Cleese cues. It's not Cleese himself, as the reflection remains after he runs out of shot to get the tree branch, and the reflection doesn't mimic every action performed on screen.
The Germans - S1-E6
Revealing mistake: When Basil is turning the fire alarm on and off, he puts the key next to the red box and turns it. However, there isn't a slot for the key to actually go in; he's just holding it close and turning it.
Revealing mistake: When Basil is climbing up the ladder to view the inside of Mr Johnson's room, he accidently peers inside Dr Abbott's room. When he starts doing his "checking" routine on the window before he falls backwards, the pane flexes, indicating that it's made of clear perspex.
Revealing mistake: There are noticable disparaties between the locations of rooms and the windows on the outside of the building. This is particularly noticable in this episode when Basil climbs a ladder to look through the window.
Revealing mistake: When Basil sneaks into Raylene's room to listen for the "extra guest" in Johnson's room, Raylene wakes up screaming. When Sybil comes in, turns the light on and Basil says "I didn't know she was there, I just came in to check the walls", look at the extreme right of the screen. You can see the shadow of a boom light on the wall.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Revealing mistake: In the scene where Basil and Manuel have put the corpse in the room behind the reception, and the Major comes over and speaks to Basil, the actor playing the corpse blinks.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Revealing mistake: Just after Polly comes down to to the kitchen to tell Sybil that Mr Leeman's dead and they leave, Basil wanders back in, to learn the news. Watch the wall on the right on the staircase when Basil shoves past Sybil on the stairs. The wall shakes so much at that point it's virtually impossible to miss.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Revealing mistake: When Basil, Manuel and Polly are trying to hide Mr. Leeman from the other guests, they put him in a cupboard. While they are talking to the people staying in the room, Mr. Leeman's hand comes out of the cupboard. Watch carefully, and you can see the actor opening the door from the inside, and then putting his arm down, making him look like the corpse.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Revealing mistake: The dog's mouth is nowhere near Manuel when he is "bit".
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Revealing mistake: When the characters are in Mr Lehman's room discussing his death, the backdrop outside the window has clear wrinkles and fold marks in it even though it's supposed to look like the outside.
