The plot is confusing and it's hard to even summarize, but I can tell you it had such elements as fear, time travel, destiny, teen romance... and how can I forget demonic bunnies and pedophiles? This movie is so far-fetched but it's one of the best (and certainly most deranged) movies I've ever seen.
And if you're wondering, Donnie Darko is the name of the main character. Poor Donnie seems a bit on the schizo side(what with seeing those demonic bunnies) but he's a great character and one of the most interesting protagonists(?) I've ever seen. And the other characters certainly add a little somethin' to the awesomely outlandish yet amazing plot.
Things just don't get any weirder than Donnie Darko.
Final Thought: Watch-worthy but don't strain yourself too hard trying to realize what's going on. I did, and now I have a headache.