DO NOT READ AHEAD UNLESS YOU HAVE ALREADY SEEN DONNIE DARKO.
THIS WRITEUP IS JUST ONE MASSIVE SPOILER!!!!!
I have written this in order to attempt to explain the movie Donnie Darko to those who have already seen it. It is an incredible movie and also a very, very, very confusing one. It took some time and research for me to figure this out perfectly. (I may just be stupid, but I can't be the only one.) If you want to figure all this out for yourself, go to www.donniedarko.com, or better yet, just watch the movie and do it unaided, if you can. If that is not enough, go to ruinedeye.com/cd. If you want me to just tell you... read on.
The unusual-sounding terms used in the following explanation are taken from the movie's website at donniedarko.com, more specifically from the text of "The Philosophy of Time Travel" by Roberta Sparrow, which is not seen during the course of the movie. Read Kawika's node for the complete text.
The bulk of the film is Donnie going through a tangent universe created for him by a higher power where he is allowed to become aware of events that would occur were he to continue living in the primary universe. Basically, his girlfriend, his mother and his sister would die. Patrick Swayze's character would get discredited. Drew Barrymore's character would get fired, etc., etc..
He is given the chance to allow his death to occur by those who die in the tangent universe, namely Frank and Gretchen, both of whom are the instruments of a higher power. Both of these characters are able to manipulate Donnie to help him reach the decision he must make. Frank appears to him as the demonic rabbit and prods Donnie in the right direction. Gretchen's manipulation is much more subtle, and is incorporated into what Donnie thinks are the normal actions of her in the tangent universe. If she, in fact, does interfere, this most likely occurs when Gretchen returns to the party after she and Donnie make love upstairs. This is the "Manipulated Dead" version of her, and not the tangent universe version. He is also manipulated in the form of the "vectors" as Noah Wyle's character describes them or "Fourth Dimensional Constructs" as the movie's website would have it.
Donnie is basically presented with a choice: go on living and the universe will be like this. Die and life will be better for everyone else. This is why Donnie repeats the line, "I promise one day everything will be better for you", to a number of people towards the end of the movie. When events have run their course in the tangent universe, he elects to resume life in the primary universe from his bed, instead of on the golf course where he is towards the beginning of the movie (the inception of the tangent universe). He is then crushed by the jet engine and life goes on... without him. The only two elements that are changed in the primary universe as a result of Donnie's decision are his location at the time of the jet engine's fall through the wormhole and said fall, the former of which comes about through Donnie's choice and the latter of which occurred through the influence of a higher power.
The director, Richard Kelly, who I now realize is a much smarter man than I, says the following in an interview from RevolutionSF.com:
I think, ultimately, it's about accepting the inevitability of fate. Accepting that there is a great master plan behind it all. And, whatever choices you make, you were meant to make those choices. And I think, ultimately, in the end, he's enlightened.
You can interpret the ending in two ways. That when he's in bed, he's laughing because he thinks it's all a dream, and he's just going to roll over and go to sleep because he thinks it's all a dream. Or he's laughing because he's enlightened because he's seen the potential, and he's had a vision, and he's accepted…. He's had a religious experience. And that's greater and better than anything that we could comprehend. So, ultimately, I hope that it would be about enlightenment, more than anything else.
The other important line that is repeated regularly throughout the movie and is spoken originally by Roberta Sparrow is: "Every creature on this earth dies alone." The one item of speculation that I will include in this explanation is in regards to this line. It may be that in Kelly's universe, every living being dies of their own free will because they are shown in a tangent universe that life will be better for everyone else because of their death. This, I feel, is supported by Kelly's statements.
The only problem I can perceive in my overall interpretation of this movie is that, were Donnie to go on living in the primary universe without the interference of Frank and Gretchen, most of the horrible events that the tangent universe presents would not have transpired. Perhaps it was simply not Donnie's place to know what the future held for him in the primary universe and he was simply shown a tangent universe that would have assured his willing cooperation in his own death. If you can think of any event that takes place independently of the actions of the "Manipulated Dead" which would make Donnie's death meaningful, please let me know. For that matter, let me know all your thoughts on this fabulous movie.