Continuity mistake: When everyone is searching upstairs and Miss Scarlet and Colonel Mustard start screaming, they all come running down. Yvette and Miss Scarlet have on flat black shoes, but right after the running shot is over, both are back in heels.
Revealing mistake: During the scene when Audrey is having a nightmare about eating too much while on vacation, the nightmare ends with her inflating like a balloon from all the food. Her blouse splits open and down the middle, where the buttons have broken, the dark balloon used for the effect is visible. (00:16:35)
Continuity mistake: During the scene where Fletch is at the hospital trying to locate Stanwyk's medical records, he drops lots of files on the floor and asks a nurse to sort them out. When he is talking to her he has a stethoscope in his ears, but when the camera moves behind him they are suddenly round his neck. Moments later they are back in his ears. (00:18:10)