Deliberate mistake: Rather than using real Bruce Lee footage only for the final fight scenes, so the undisguised Billy Lo's different appearance might make sense after his surgery, the filmmakers instead spliced real Bruce Lee face footage throughout the early film giving the character a constantly changing face from scene to scene.
Deliberate mistake: Poirot riles up Pennington narrating the story of Grand vizier Ptahhotep who was crushed under the weight of the silver he embezzled. It's a lovely moral story, but Ptahhotep was actually a virtuous administrator and is credited (with various caveats) with writing "The Maxims of Ptahhotep", one of the first books in human history, and there's no record of such a story. It's likely that Poirot made that part of the story up counting on Pennington's ignorance on the subject. (00:44:20)