When Basil stops in his car because the street is blocked, the street is dry, but when he backs up and the car dies, the street is wet from rain.
When Manuel fetches Basil to answer the phone, Basil enters the hotel first, followed by Manuel, but when the camera viewpoint changes to the interior, Basil is following Manuel.
When Basil goes to get the branch, after the car breaks down, the car jumps onto the pavement between shots.
The number plate of Basil's red Austin 1100 Countryman changes in different episodes. In Gourmet Night (1975) the car's number is WLG 142E while in Basil the Rat (1979), the car's number becomes OYF 747R.
When Basil's car breaks down for the final time after reversing away from the van, the garden gate of the house next to the car is open and it swings shut just as Basil says, "One, two three." The gate was shut when he first reversed around the corner, but was open again after the shot cuts back to the car (after it's moved to the right along the pavement).
Just before the famous 'car thrashing' scene, Basil drives from Lapstone Gardens into Mentmore Close where, stopped by another parked vehicle, he is forced to back up and the car thrashing scene ensues. Had he not been blocked, he still wouldn't have got very far entering a dead end.
After they discover the chef is drunk and Basil pulls Manuel into the kitchen, a large gap between the edges of the walls is clearly visible.
It has been established from the script that the events are set in either autumn or late summer. The gourmet evening is running seriously late by the time Basil has to visit Andre's (twice), yet when it should be either twilight or dark outside, Andre's is set in broad daylight with almost no shadows.
When a drunk Kurt howls "Manuel!" and pushes Basil flying across the kitchen, Polly is standing in the background covering her face in despair. As Basil returns, the camera catches Connie Booth for one brief moment, clearly trying to suppress a laugh.
As Basil asks Kurt for instructions to cook mullet, he holds the food under the chef's drunken face. Kurt's reaction was to be sick all over the plate of fish. Whilst in front of the live TV audience the barf was actually performed, it was never to appear in any further transmission, presumably considered too disgusting. However, there are two clues to the presence of this edit. Looking carefully at Kurt's face before throwing up, it is obvious he has a mouthful of prop-vomit ready to release, and secondly, the audience's reaction to what was edited out can clearly be heard, as a jump-cut to Sybil's reaction replaces any view of Kurt's unfortunate puke.
When Basil impersonates the duck, the sound effect used continues when his mouth is closed.
When Basil is trying to repair his car and tries to start the engine, the engine sounds are out of sync with Basil turning the ignition key.
Whenever Basil is trying to start his car, the car's starter motor is cranking steadily and continuously, yet often it is clearly visible that Basil is just twitching the ignition switch on and off, not holding it in the "start" position.
When Basil is talking to Sybil about distracting them, he tells her that Andre is cooking duck for them because Kurt is unconscious, he starts making duck noises. But when he arrives back into the bar where the guests are sitting, he continues making noises a second later when his mouth has stopped moving.
When Basil attempts to go through one of the swinging doors, leading to the dining area, but slams into it, when the doors do finally swing open a crew member is seen crouched down in the corner.
A stage hand is clearly visible twice, crouching behind the double doors into the dining room. Once as he is causing Basil to hit the door and drop the duck, and a second time as Manuel enters the kitchen. His dress is clearly dissimilar to everyone else's' and he looks directly into the camera, causing the cameraman to quickly pan right.
When Basil is out of the car and shouting at it after its final breakdown, a crew member is reflected in the right hand side of the windscreen, giving John Cleese cues.
After Basil gets the duck from Andre, he tells Manuel to get the trolley. Basil then walks into the door, and the duck goes flying. An arm of a crew member is holding the door closed. When Manuel comes through the door and stands on the duck, the crew member's face is visible.
When Basil follows Manuel into the hotel, the shadow of a crew member holding a boom mic can be seen bottom right as the camera follows them across the terrain.
When Basil runs to change the menu and Sybil says, "Why?" a shadow of the boom is visible on the pigeonholes at the side.
When Basil walks into the kitchen and asks Kurt for the bottle, the shadow of the mic can be seen against the wall in the upper right corner of the screen.
After Basil screams his threat at the car to "start in three seconds or else", he does not crank the engine during that time; he just sits there and hot-headedly counts off the seconds, without trying to start the engine again.