John Cunningham created the motivational doctrine that everything exists on a continuum between Fear and Love, and as a consumer and possible creator of child porn, he can be said to simultaneously embody both extremes.
In the Director's cut, the song Love Will Tear Us Apart by Joy Division is heard playing diegetically during the party scene. The version of the song used is the re-release from 1995, despite the fact the film was set in 1988. This seems like it could be a mistake, as a record released in 1995 couldn't be played at a party in 1988. until you remember that the entire film focuses around the concept of time travel.
Similarly, when Donnie is talking about Back to the Future to his physics teacher, he refers to how much he liked their depiction of the future. The future was only shown in the second movie, which came out in 1989, a year after the events of the movie. (The fact that his teacher is giving him a strange look as he describes this suggests this isn't an error.)
The version of 'Love Will Tear Us Apart' as heard in the film was indeed released in 1980, as a B-Side of the original single.
If Frank had never talked to Donnie, Donnie would have died immediately and there would have been no time loop. So, the entire purpose of the movie is to give Donnie the chance to come to terms with his death. Seems a LOT less of a downer when you realize that it's not a movie about being screwed no matter what you do, it's a movie about getting the chance to accept and see the meaning in your would-have-been senseless death.
The random comedy of the Smurfs conversation can distract from an important bit of foreshadowing in that scene, especially relevant since they're seated only a short distance from Grandma Death's house, which is that Donnie is a very good shot with a rifle.
Donnie Darko had a doozy of one at the end. Think of it: in this timeline, Donnie died without going on his murder-and-arson spree. Thus, he never burned down Jim Cunningham's house, thereby exposing the fact that Cunningham was making child porn. It's never insinuated that Cunningham would be found out any other way, and in the meantime, the head coach of the little girl dance team adores the man and trusts him completely. If he asked to give the girls a 'private lecture' on Love vs. Fear, she wouldn't bat an eye. In conclusion: Donnie's death will almost certainly cause his little sister to be molested.
Actually I heard that Cunningham killed himself soon after the night Donnie died.
I believe on the website you can find a newspaper clipping on Cunningham's suicide a couple of weeks after Donnie's death.
While we're going there, seems more likely that he might well have gained access to the dance team before the events of the movie, and maybe Donnie knows or suspects something already, explaining the level of hostility he displays toward Cunningham (which otherwise does seem a little disproportionate).
Rather more of an extreme Fridge Tear Jerker, but Donnie's conversation with his mother at the beginning is the last thing he ever said to her. The last time she ever interacted with her son ended with him calling her a bitch.