Continuity mistake: In the beginning when Col Mustard shows up, the butler shows him to the library, you can see that door to the library is open. When the scene shifts Wadsworth is opening the door. (00:05:30)
Other mistake: Even though it is pouring with rain, Mr. Green's coat is completely dry when he arrives at the manor. (00:07:30)
Character mistake: During the conversation in the study about who is blackmailing who, Mrs. White mentions two of her five husbands: An illusionist who disappeared and never reappeared and a nuclear physicist who was found dead at home. During the last ending, Mrs. White says "So this has nothing to do with the disappearance of my nuclear physicist husband or Colonel Mustard's work on the new top secret fusion bomb?". However, during the conversation in the study, Mrs. White says her illusionist husband had disappeared and her nuclear physicist husband was found dead at home. So the correct term would be "So this has nothing to do with the disappearance of my ILLUSIONIST husband or Colonel Mustard's work on the new top secret fusion bomb?". (00:21:05 - 01:27:35)
Suggested correction: Ms. White's nuclear physicist husband disappeared too, so the line is right.
Audio problem: In the scene where everyone gangs up on Mr. Boddy, the audio doesn't match much of the action going on. (00:23:10)
Continuity mistake: Miss Scarlet moves to a table to open her unexpected gift. When she says "I enjoy getting presents from strange men", if you look close enough, she goes to remove the box's ribbon twice. (00:24:45)
Continuity mistake: Before Mr. Boddy turns out the lights, there is a statue a few inches below and away from the switch. However when Mrs. Peacock turns the lights back on, the statue is directly under the switch. (00:26:25)
Revealing mistake: A visible editing flaw occurs near the beginning, after they return from the Billiard Room with Yvette. While Mrs. White is saying her line to Wadsworth, "I think you had better explain," she starts to unbutton her overcoat. Next is a wide shot of the room that is supposed to be in real time, but Mrs. White's overcoat has already been removed, and she is getting ready to lay it on a chair. Everyone is paused on their marks as if the film was spliced at the exact moment the director yelled, "Action" and no one had moved yet. (00:31:12)
Continuity mistake: When the Cook's body falls out of the freezer on Mr. Green, he is pushed onto the floor. In the next shot, he is standing back up again. (00:33:20)
Deliberate mistake: When they are bringing the Cook's body into the study, it's obvious the Cook is actually the Cook's double because she is much thinner and takes up less space in the doorway. (00:34:40)
Continuity mistake: Colonel Mustard pours everyone a drink, he puts the whisky on the table and in the next shot the glass he poured whisky in is in his hand without enough time to pick it up. In addition, he puts the decanter down closer to him in the close-up, than it is in the medium long shot. (00:41:15)
Continuity mistake: When everyone is in the Library, you can see the matches in a cup on the left of the fireplace. When Professor Plum says, "Wait a minute, suppose that one of us is the murderer," you can also see that the matches are in a "V" shape. When Wadsworth walks towards them to pull the matches out, most of them are all leaning to the left side of the cup. As the movie goes on, when the cop gets locked up in the Library for the second time, the same amount of matches are in the holding cup as if Wadsworth did not pull them out and they are in a straight line. (Third time code 1:02:40). (00:44:25 - 00:45:05)
Visible crew/equipment: When Mrs. Peacock turns on the cellar lights, a piece of lighting equipment is visible to the left of the screen. (00:47:45)
Visible crew/equipment: When the cop is driving past the broken down vehicle, a crew member's arm can be seen reflected on the car. (00:49:35)
Deliberate mistake: When the chandelier smashes after Colonel Mustard and Miss Scarlet are freed from the lounge and at the end of the first ending, the light level doesn't even go down. (00:53:15 - 01:20:30)
Audio problem: When Yvette shows everyone the open cupboard and the door bell rings, Professor Plum turns his head before the door bell even rings. (00:54:00)
Revealing mistake: When the 4 people upstairs, Yvette, Mr Green, the butler, and Mrs White all come running downstairs because Col Mustard and Mrs Scarlet are yelling at the locked door they collide at the top of the stairs. When they all hit they're stunt men and women. (00:54:15)
Continuity mistake: When Mr. Green is showing the cop the dining room, you can see the hallway is completely empty. In the next shot, Professor Plum and Miss Scarlet are half way between the study and the lounge. (00:57:55)
Deliberate mistake: When Mrs. White is screaming after the power cut, she then says "Help me!" multiple times. It's obvious the "Help me!" lines are just a recording played over and over. (01:03:15)
Other mistake: When everyone finds the Cop's dead body, there is a wound showing were the murderer hit him on the head with the pipe, however, the pipe shows there is no blood. (01:04:30)
Continuity mistake: The Singing Telegram's body position changes when everyone finds her. (01:04:45)
Suggested correction: She was shot, not switched off. She likely didn't die instantly. It's perfectly reasonable that she would move her arm as she was dying.
She died instantly, that is why she collapsed instantly. I am still wondering why they didn't make it look like a real shot, and have blood around the area she was shot at? They made it look as though she was wearing a bulletproof vest and was shot. You can see silver, no blood.