A different angle: Frank is an evil one, sort of Bob from the Twin Peaks!

Rating: 10/10 (16 June 2007)

Donnie Darko is my Top 3 movie of all time. It is similar in its impact to the Mothman Prophecies with its dark optimism, but way bigger.
I haven't read The Philosophy of Time Travel yet, but saw vague allusions to Twin Peaks, and came up with a different approach to the plot. The idea of "corrupted" Universe being "fixed" by Frank through weird acts has its grounds, but after all black holes and E-R wormholes are permanent phenomena and don't necessarily imply on "corruption" of the (infinite) Universe. These portals simply exist, and some beings can make use of them.
I think Frank on one side is a thoughtful serial killer who enjoys his supernatural powers and plays with people and their dreams the way he wishes, spies after them, push them to death and even kill some here and there. On the other side he's a young guy that has a name and even a girlfriend (his cover).
Franks says, his male ancestors were named Frank, and judging by Ed Darko's comments on a bed in the hotel, a guy named Frankie died on his way to a teenage party in days of D's parents' youth (strange coincidence!). So it is probable that Frank's clan has always been doomed to die of young age (early 20s, it seems). Knowing this, F might have tried to cheat his own future too or maybe even was a multi-dimensional thrill ride freak (like in "Retroactive")! I might be wrong, but Frank looks a bit like a native Indian to me, which only adds to "the other reality" spice, ensuing typical means of interacting with it (hinting on Don Castaneda and Indian magic and all that there is in altered states).
Suppose Frank is a being similar to Bob from Twin Peaks. Is F a good guy? Over the course of the movie I couldn't find any proof to that. He's got some Master Plan of his own, and only the events and end results reveal his real nature: a spider playing with a fly. Franks is an ESP being that sees the world in 4D, and he lives in both realities and is also capable of reading other people's minds and affecting them through their dreams. That is he exists in many realities and it's even hard to say which one is real. I'd even call him an eternal being that sheds his skin and cheats his fate or plays games with it. He is also capable of sharing his enormous powers by inducing those in his preys as well (Donnie's power to be invisible, drive an ax deep inside solid bronze sculpture etc.).
The movie more or less delivers 3 "time loops". Loop 1 ends in the episode with the plane engine fall in Donnie's room. Loop 2 can be called "Frank playing the cat-and-mouse game with Donnie"  finalizing with death of G & F (and possibly Gretchen's mother + Rose, Samantha and those on the plane, too). Loop 3 realizes Frank's plan with eventual death of D from the loop 1 engine. In the end we see F still alive (sitting on the floor touching his right eye as if to check that this time it's there  so he's won, the game's over). G is also alive.
If Frank would have wanted to save D (and D believed he would), he'd have done it. No matter how you turn it, the cause of all Donnie's troubles in loop 2 is Frank. That's why the theory that he's a serial killer in a rabbit's suit (or the one trying to escape his own death in loop 2) appears plausible to me.
D is not sick, he's pretty sane and is much smarter than most of his peers, but he's affected by F most of the time. The treatment he gets is water placebos and useless talks with his shrink. I can easily suggest that Frank KNEW that in one of the possible realities (universes) Donnie would kill him after death of Gretchen. And F could manipulate/ foresee the events, let's not forget that. When D+G were happily sitting in the movie, the Manipulated Dead Frank (with the already smashed eyeball  which he kept hidden behind the rabbit mask from the very start) asked D to forgive him ("I'm so sorry"  for killing G!) and soon D FELT (thanks to his superpowers) that F was "going to kill" someone (hypnotherapy episode  but he didn't know WHO the prey would be).
Now what if F enjoyed using his superpowers and simply played with objects and people as a crazy juggler? What if he was an evil being who simply drove others to craziness or death? He had known beforehand that in THIS reality he'd eventually get killed by D after hardly unintentional (F could see the future!) killing G! He didn't want to end up like his ancestors and he started playing that fishy game. He played "saving" D and the Universe on one hand only to reverse the situation and kill G & D. It slightly resembles of Bradbury's "A Sound of Thunder" (doomed to die T-Rexes are hunted on by thrill-loving guys from the future). And if we weigh positive and negative end results, the bad outweighs.
Re. R.Sparrow. She's gone through some experiences of 4D nature (as a heavily praying nun she might have found herself in an altered state or gained the ESP abilities. She simply KNEW about the parallel universe(s) and saw things and tried to explain them, but couldn't change/ affect things or people, it seems. And ended up in seclusion and mental disability with the only thought that someone would send her a letter (clairvoyance). Again, if she'd be sane or as powerful as F, she'd somehow save G and D (and don't forget: she after all caused F make a turn resulting in killing G!).