10 Movies You Must Watch 1000 Times To Spot This
2. Doc's Shirt Foreshadows The Third Film - Back To The Future Part II

Any self-respecting film buff has seen the Back to the Future trilogy more times than they've had hot dinners, yet all but the most committed fans will have largely missed this ingeniously hidden-in-plain-sight feat of foreshadowing.
Early in Back to the Future Part II, we see Doc (Christopher Lloyd) wearing a patterned white, blue, and yellow shirt, but what you probably didn't notice is that the design actually depicts cowboys on horseback chasing a train.
Gee, doesn't that sound familiar?
Back to the Future Part III of course shifts the genre to a Western, where horses and especially trains play a major role in the story.
And so, while the end of Part II does include a brief teaser trailer for Part III, the sudden shift of genre was masterfully hinted at much earlier in the film.
But it gets even better, as in Part III Doc actually uses the very same shirt as his bandana when performing a stickup.
As much as shooting two sequels back-to-back has the easy potential for disaster, it also allows for fantastically cohesive foreshadowing and callbacks like these.