Visible crew/equipment: When Frank is loading the lorry at the warehouse, he drives the forklift onto the lorry, then the lorry drives off while he and the forklift truck are still on the back. As the lorry pulls away you can see the camera crew on the other side of the road filming the next shot.
Revealing mistake: When the second piece of scenery falls on Frank, it has a tear halfway down and a hole in it that Frank's head goes through. A few seconds earlier, these weren't there. Maybe they were put there to make sure Frank's head went through, or else this is the second take.
Continuity mistake: When Frank is demonstrating his star trap to Father O'Hara, Frank comes up through the stage floor too fast and grabs hold off a length of material stretched across the top of the stage which falls down onto the stage floor when Frank falls, but in the following shots of the scenery collapsing this piece of material has disappeared.
Continuity mistake: Mr. Finney is explaining the mirror signal manouver procedure to Frank during his driving lesson in the white Mini. While they are parked, the shots from inside the car show a line of parked cars behind the white Mini. But when Frank moves off, the shots from outside the car show no cars parked behind the Mini.
Continuity mistake: When the mini goes into the horse box, Frank is on the roof. When it stops, Frank is thrown onto the horse's back. But when the car first goes into the horse box, there is no horse inside it. Also, you can see the ramps put on the tailboard so the car can drive up it. They fall away as the horse box drives off.
Continuity mistake: When Frank is taking his driving test in the Hillman Imp, he is driving slowly down a narrow and winding road. He is being followed by the green van, flashing its lights at him, and as the van turns off Frank hears a train hoot, then drives round the barriers at a level crossing. The terrain suddenly changes from a narrow road in the hills, to a wide road on flat land. Then while Frank is driving to the sea, he passes the same parked brown Vauxhall Victor twice.
Continuity mistake: When Frank is driving the white mini in the country lane, trying to overtake the lady on the bike, there is nothing behind the mini, but then a split second later he is being followed by a silver Renault. As he tries to overtake the cyclist, Frank is followed by a brown Triumph, then a second later a yellow Ford Anglia is following him. Frank also appears to drive along the same stretch of road several times, as he keeps passing the same parked cars.
Revealing mistake: While Frank is taking his driving test, he and Mr. Hayes are wearing standard road safety belts in the car. But when the car is in the sea after crashing through the fence, both the occupants are wearing motor racing type safety harness obviously fitted for the stunt.
Revealing mistake: When Betty goes into labour in the night and goes downstairs with her suitcase, she tries opening the front door. You can see it moving with her pulling. And then when Frank goes to climb out of the window to follow the key, he climbs onto the sink, which almost rolls away, which reveals the fakery of the set.