Chekov’s Gun. Set up and payoff. “If it’s not essential to the story, don’t include it. Named after Anton Chekov.
Lots of great examples in fiction. Indy’s fear of snakes. The power loader near the beginning of Aliens. Q’s gadget briefings to 007. Basically all of Back to the Future.
So my question is are there any examples of where something is seemingly set up to be a Chekov’s Gun, but then nothing ever comes of it?