Revealing mistake: When Charlie and Grandpa Joe drink the fizzy lifting drink and are floating in the air you can see the hook that is connected to the wire that Charlie is being held up by.
Continuity mistake: Vera gets onto her bus just after Stan and Jack have put spiders in the cab. She is wearing boots when she discovers the spiders, causing her to run into the back of the lorry. As she does so, it is evident that she is wearing shoes.
Plot hole: The police Inspector recounts the murders, comparing them to the ten Biblical plagues of Egypt, and he states that in keeping with this theme Dr. Kitaj was killed by rats. First, Dr Kitaj dies in a plane crash. Okay, he was attacked by rats in flight but nobody would know that - his plane crashes in a huge, violent fireball and nobody would find any rat remains after that. Second, there was no plague of rats in ancient Egypt! (Go ahead, look it up). Even if the police had made the connection between the mysterious deaths and the ancient plagues they would not make the connection here.
Continuity mistake: Polly Browne is in her dressing room with a picture of Tony Brockhurst on her mirror. She starts to sing and picks the picture off the mirror. As we see a close-up in her hands it is a totally different picture of Tony. As she puts it back, the photo has reverted back to the original.
Visible crew/equipment: At the end of the film when the women have broken up the strike, after everyone has gone back in Sid James and Hattie Jacques are standing talking in front of Sid's car you can see the boom mike reflecting in the window of Sid's car.
Audio problem: When Woody Allen is driving in his car, he is talking to himself. In the next shot, when the car is shown farther away, you can still hear his voice talking, but his mouth isn't moving.
Continuity mistake: When Sandy takes out a condom in bed with Susan, her hair changes between shots.
Revealing mistake: When the platoon hear the church bells, they mistake it for the invasion signal and construct a barricade across the high street. If you look behind them you can see cars parked on the road in the distance that date from well after the 1940s.
Revealing mistake: A 'bald wig' is visible on Harry Morgan when he first arrives in Purgatory.
Visible crew/equipment: When Maude pulls the banjo out of a cabinet, you see the reflection of crew and lights.
Continuity mistake: When Gran first dangles down from the ventilation shaft, the slaver's key ring is too wide to fit through the opening. But when Jim loses his balance and Gran is jerked back into the cell, the key ring is suddenly much smaller than before.
Revealing mistake: Just before Hermie goes into the drug store to buy the condoms, you can see his breath when he is talking even though it's supposed to be summer time.
Factual error: When Lurcio is dragging his ass through the market he passes several stalls which stock fruits and vegetables totally unknown to the Romans - potatoes, corn, papayas, mangoes and breadfruit amongst them. They were unknown in Europe during the time the film is set, and the Romans did not trade with anyone who knew about them, either.
Other mistake: When the Mayflower truck is on the move picking everyone up for the heist, a mysterious hole appears above the truck's cab, cut out in the letter "o" in "Mayflower" when Pop is picked up, that wasn't there a moment before, and then it vanishes. The same thing occurs after the heist, when the truck crashes into the police cars.
Continuity mistake: When the farmer threatens Henry VIII with a fork after he catches him in the barn with his daughter, you can see that Henry is holding on the fork and it is well away from his body, but in the next shot the fork is pointing near Henry's face.
Audio problem: When the saxophonist talks to Eddie (Albert Finney) before joining his band, which has already started playing, the saxophone can be heard although the player has not yet joined them on stage.
Continuity mistake: During the wedding sequence when Walter Matthau is trying to force his daughter Mimsy out of the bathroom his vest is closed with his tie inside. The next second the vest is open. Then it switches back to being closed again.
Visible crew/equipment: When the kids are singing "All things bright and beautiful" you can see the shadow of the hydraulic camera. (00:15:15)