Only a few years ago did I notice that Darth Vader’s helmet wobbles in the wind while he delivers the “search your feelings” line (and the rest of the scene until Luke falls) in ESB.
It’s become for me one of those; once you’ve seen it you can’t unsee it moments.
Or the bit where Luke leaps down from the Carbon Freezing platform and bounces off a little trampoline…(I didn’t spot that one, I read it somewhere)!
Oh, yeah, I’d forgotten about that. Thought he wasn’t on a trampoline. Hamill simply lands on the ground after a very short jump and his head briefly pops up into the lower frame as he stands up again, and then we hear the landing sound effect afterwards.
I actually did notice that one on my own a long time ago. I don’t remember exactly which version it was I noticed it on, though it was definitely the original version (either VHS or GOUT DVD) and I remember the image was bright enough to make Luke’s head popping up before the landing sound effect was fairly obvious. As someone who’s always been very interested in the craft of film-making, it was always fun to notice small errors/quirks like that.