Revealing mistake: When a dangerous cobra threatens some stand-in wearing Poirot's pants, under the sink you can see the reflections on the protective glass. (01:25:50)
Revealing mistake: After Poirot has inspected the messier of the 2 bottles of nail polish he has a laugh with Race (it almost looks like Ustinov and Niven are breaking character at the end of the shot) and they briefly pass through the murder scene again. Look at Lois Chiles' eyelashes; she's blinking, not quite dead. (01:12:20)
Revealing mistake: When Poirot gives the sarcastic explanation of the letter J to the doctor and colonel Race, the chest of the stone-cold dead Linnet quietly rises and falls as the very alive actress breathes. (01:08:35)
Revealing mistake: 'Uncle' Andrew Pennington reads the article with Linnet's wedding. The article is obviously fake; the part about the wedding is written in a font different from the rest of the page, and the rest of the content resumes without any column break. (00:08:40)
Revealing mistake: Jackie is so ecstatic at the idea that her boyfriend is going to work at her friend's estate that she kisses him without watching the road. Since she is not paying attention, the car nearly hits the hedge at one side of the road, and she does a last minute swerve ending up cutting through a lawn before she can get back on the road again. During this maneuver which should be spontaneous and unplanned, you can see dirt skidmarks on the asphalt in front of the car from previous takes and a clear pathway through the lawn. (00:07:30)
Revealing mistake: The Manager Of The Karnak Mr. Choudhury excitedly shouts "goody goody gumdrops" when the crew fishes out from the river the incriminating package. He then runs across the deck to bring it to the investigators. As he does that though, you can see on the floorboards already a wet trail from a previous take. (01:29:45)
