Unmarked spoilers are ahead, per Spoilers Off rule.
The original 1941 novel:
Regarding Mrs Gardener and Ms Brewster talking at the same time: "The result sounded rather like a sheepdog whose short stentorian barks interrupted the ceaseless yapping of a Pomeranian."
"The eyes of Hercule Poirot dropped somewhat ruefully to a certain protuberance in his middle."
The 1982 film:
The Passive-Aggressive Kombat between Daphne Castle (Maggie Smith) and Arlena Marshall (Diana Rigg):
Daphne: Arlena and I were in the chorus of a show together. Not that I could ever compete. Even in those days, she could always throw her legs up in the air higher than any of us. And wider.
Arlena: Kenneth, this is such a surprise! When you told me of an island run by a quaint little landlady, I had no idea it was Daphne Castle.
Kenneth:(embarrassed) Er, yes, quite. Daphne, I wonder if we could go to our rooms. It's been a long journey.
Daphne: Oh, certainly. (rings the bell, and calls out) Andreas! (no response)
Arlena: If you're short-staffed, Kenneth can easily carry the bags.
Daphne's response to Arlena's late arrival at the evening cocktail gathering:
Arlena:(making a grand entrance) Oh my, I'm the last to arrive!
Daphne:Have a sausage, dear. You must be famished, having to wait all that time in your room.
Kenneth Marshall mentions that the cannon is fired every day at noon in commemoration of a 10th century victory, apparently the only remarkable feat in their entire history.
Poirot puts on his very The Roaring '20s swimming garment (to a triumphant fanfare), and makes an elaborate show of getting ready to go in the water... and chickens out.
After Patrick Redfern has been outed, he socks Poirot a good one in the jaw.
When Daphne Castle tells Poirot (who is recovering from being punched to the floor) that he has been decorated with an award from the King of Tyrania:
Daphne: He is so pleased he is awarding you the Order of Saint Gudrun the Inquisitive.
