The fire alarm that plays such a pivotal role, prominently placed at the reception desk, is mysteriously absent in all other episodes.
During the fire drill Mrs Wilson's shoes are different when she is outside the hotel to when she is inside the hotel.
During the fire drill, the guests insist that the burglar alarm is indistinguishable from the fire bell. Immediately after they claim not to have heard the fire bell.
Assuming conflagrations aren't an everyday part of life at the hotel, there's an awful lot of scorching at the back of the kitchen and on the oversized gloves Manuel (oddly) wears to cook chips in a frying pan, indicating that there was at least one retake.
As Basil Fawlty flees the doctor who wants to sedate him, a studio monitor can be seen in the background, complete with the same image that is on the screen.
The hotel is supposedly located in Torquay, yet the hospital where Sybil is staying is Northwick Park Hospital according to the sign outside. Northwick Park Hospital is in Middlesex in North West London, miles away from Devon.