I've been watching and enjoying Back to the Future for nearly twenty years now and it still amazes me that I can think of new paradoxes and complexities regarding the detailed plot and I've always wondered just how much thought went into the screenplay or is it just another case of analyzing a film too much and reading into it things that aren't really there. I wonder how much of the plot will be discussed by Bob Gale and Robert Zemeckis on the DVD commentary tracks. Here are some points I'd like them to touch on. Spoiler alert for the rest of this post. I remember the first discussion was about whether or not at the end of the film, when Marty sees himself go back to the future, did he create a shadow while he was near the Mall sign that is visible at the beginning of the film when Doc gets shot. If so this would be one of several clues in the film to indicate that Marty had already time travelled before the events of the film. Some other clues are: Doc is clearly wearing a bullet-proof vest in the beginning because there is no blood when he's shot and in the opening scene with the clocks there is a clock replica of the clock tower complete with a miniature Doc hanging off of its hands. That last one could be considered an inside joke by Zemeckis. If anyone here remembers the articles that appeared in Starlog magazine written by Bruce Gordon then you'll recognize some of this discussion. I won't get too into this unless I see enough people want to talk about it because I could go on forever about this. I'll mention a few more things about the first film. I won't even get into the second and third movies yet. I've wondered about the second Marty at the end of the film the one the first Marty sees take off at Lone Pine Mall. We can probably assume that Doc was smart enough not to tell him anything about going back in time after all he was busy inventing a time machine under the immense pressure to finish it before October 26, 1985 for the unveiling at Lone Pine Mall. We see Marty watch himself go back in time. Well, that Marty has hip parents and family and Biff is a servant to his Dad, who also happens to be a brand new sucessful author. When this second Marty goes back he would have to do everything exactly the same as the first Marty without changing anything just so his future is as he left it. We know some things will be slightly different like the photograph of his siblings. I was also thinking that maybe the Doc could return the favor for this Marty for saving his life by secretly hiding an extra vile of plutonium in the car and leaving him a note to find after he's in 1955 so could come right back. But this might prevent time travel from being invented in the first place because: did Doc invent it or did Marty tell him about it? It's the chicken and the egg. Which came first. Certainly if he came right back his parents would be nerds without his interaction but who knows what they were originally. Only the writers know. The only way we'd know that it was the first time travel experiment is that Doc would actually die with blood everywhere. I'm wondering how many pine trees old man Peabody had on his farm initally. 88 maybe? It seems that every time Marty goes back he knocks down one more. I'd love to discuss this more if anyone's interested especially my theories on the ending of Part I/beginning of Part II and why they are subtly and no so subtly different.