There's one thing about Back to the Future that hasn't been analyzed yet just looking at that list---the changes they made to the original script that made it great. In the original script, Marty didn't travel in the Delorean....he was merely sent back. I think Zemeckis realized that it would be more dramatic if they used an off beat car in a thrilling chase--and he was right. There are others that made a messy first script into a classic. I think the real reason why people love that movie so much is they can relate to it and see themselves in it. Who wouldn't want to go meet their parents and change their past? Zemeckis also skirted the line of giving us what we want (familiar obvious elements we'd expect) and also made it seemingly fresh like we haven't seen anything like it before. A virtually impossible feat to accomplish. I'm still marveling how he setup and paid off everything as well as he did.

Paul, it's super instructive to compare the 1984 final draft of BTTF to earlier ones. The first one which you mention dating from 1981 is WAY different than the movie. I'll post some of those differences in the OP. It's a testament to the rewrite process as Gale and Zemeckis kept working the material over and over, and along the way, came up with dozens of setups and payoffs. The script really is a marvel.

From what I remember, in the original draft the time travel back was pretty static. Marty just somehow traveled back without much context. In the rewrite, not only was the added car chase and motivation (pursuing terrorists) added, but the wonder of when he first appears in 1955. Most of the changes seemed make the scenes more dramatic and put them in positions where more naturally comedic elements are bound to happen. The lines were funnier too.

Interesting list Scott. Just curious....didn't Zemeckis and Gale also make the scenes more urgent.... I remember Marty kind of just wandering around as if the writers were just first exploring time travel...in the rewrite, it's urgent from the get when they arrive at 1955....and also Marty's responsible for keeping his parents apart and his mother falling in love with him.

It's been years since I read the earlier drafts of the script, but yes, I do think they increased the pressure on Marty in the movie on several fronts. If I can grab some time, I'll give both the earliest draft and shooting script a read, draw some comparisons.