Continuity mistake: At the beginning of the opening credits, there is a close-up of the model boat pushed forward. It passes by a kid who is hunched over, hands on his thighs. Wider shot, and the kid just watches the sailboat pass by standing apathetically. (00:02:15)
Continuity mistake: Sitting on the park bench, Japp narrates the jewelry heist to Poirot. The passersby during the scene change in the various angles, and the most evident demonstration is offered by the fella that starts his walk exactly when Japp sits down. Grey pants, a sleeveless vest and hat, he walks all the way to the path in the background and exits stage right. But he's walking behind Japp when he says "The stones in his pocket were not the real stones." (00:03:00 - 00:03:45)
Continuity mistake: When Poirot and Hastings enter the Athena, there's an establishing shot as they walk to the right of the concierge. In the following shot, some elements like the lady with the flower dress by them are consistent, but the desk employee is suddenly on the phone and a bellboy appears by the stairs. Also the lady in the corner changes from a blonde to an elderly woman in a red coat. (00:05:50)
Continuity mistake: Poirot tells Miss Lemon to calm down because "It is only the simple blackmailer." Pauline Moran has her right hand on the bag, but in the close-up that follows her hand is at a distance from it. The difference in position (and thus in the takes being edited together) is reflected by a mistake happening a few seconds later, when you can notice as she turns around to answer the door, that her gloves have also switched hand. (00:12:10)
Continuity mistake: Lavington puts his hat on the couch before talking to Poirot. The hat shifts closer to Hastings and then back closer to the armrest during the scene. (00:12:45 - 00:14:30)
Continuity mistake: Lavington arrogantly sits in Poirot's study and opens his cigarette case, closing it after. In the following close-up, the case is open again. (00:13:15)
Continuity mistake: When not-so-Lavington is spying Japp and Mad Dog Poirot outside of the station, he is holding the wheel with his right hand at the top, but a moment after he's using that hand to smoke instead. (00:34:35)
Continuity mistake: When the box opens revealing the jewelry, the jewelry is scattered differently each time it is seen. The box itself gets closer to the table's edge when the lady nabs the jewelry. (00:40:40 - 00:42:40)
Continuity mistake: When Gertie and Joey make their escape running down the stairs of the hall, they pass by a couple (she has a white hat and a blue dress). When Poirot and Japp run after them, the same couple has jumped back several meters. (00:43:00)
Continuity mistake: The cream colored shoes of the Lady are prominently featured in the finale. When the actress has to run, not only are the heels replaced by modern tennis shoes, but they're black, in contrast with her white stockings. (00:46:40)
Answer: He definitely says "Belgian", but the subtitles get it wrong and show him saying "American."
Wblank71