https://moviechat.org/tt0090605/Aliens/6127a1a24f3d185137134a2d/Sequels-where-the-main-character-gets-a-new-trait-but-its-always-been-there
Of possible interest to this board.
That's an interesting comparison. I sometimes think people overegg the "chicken" thing, it is possible someone could have a quirk like that which doesn't happen to show up for a while, but I admit it is jarring and something I noticed even as a kid.
I love II & III and consider them to be among the if not the best sequels of all time, and in *some ways* I prefer the second to the first, but I've got to admit they do have some elements that are clunkier than anything in the first. Similar to "chicken" Doc suddenly picks up a catchphrase about "Thinking forth dimensionally" in the third film. Mostly some of the foreshadowing is kind of clunky; showing Marty ace that gunslinger arcade game is a nice touch that pays off well, as is having Biff watch Clint Eastwood, but why would a glossy puff-piece Documentary about Biff talk about his wild west ancestor? And 1955 Doc has a fairly jarring mini-speech about his love of Jules Verne at the start of III, even though it comes up pretty naturally later in the film.