Back to the Future is remembered fondly for a great many things. Well, mostly hoverboards. For its time, the special effects were very accomplished, though the best ones, the ones that required the most effort, aren't the most flashy. In fact, you won't believe the co-ordination that was required just to get the first three minutes of the movie just right, as you'll see broken down in the video here.
Documentary maker Jamie Benning recently interviewed Back to the Future's effects supervisor, Kevin Pike, who was happy to explain everything that was going on behind the scenes for the movie's opening. Shot in one continuous take, every detail, from the running clocks and smoking toaster, to the robotic dog food machine, had to operate without a hitch:
Some of [the clocks] worked, some of them didn't. The ones that didn't had to be made to work, or look like they worked. The ones with pendulums — we had to swing those. We had to hold certain parts of certain clocks from ticking and going forward too soon, we had to reset all of them back to number one and then hold them until they called action. We had about 20 guys behind the wall operating the clocks alone.
For a movie about time travel, you can understand why they'd want to pay close attention to the clocks. It's amazing to think of all the preparation that went into such a short sequence.
Note that this clip is part one in a series, though you'll have to wait for the others.