One thing about this movie doesn't make sense (okay, maybe more than one thing, but the guides at salon.com help a lot). Leonard tells Teddy at the end that his wife didn't have diabetes, but it's also said that he remembers everything that happened before the accident. If Leonard is the "real" Sammy Jamkins, shouldn't he remember that his wife has diabetes, and therefore know he's been fooling himself?
The whole point was that he was not thinking rationaly.
I don't think it's that he wasn't thinking rationally, it's that he conditioned himself to believe that those actions were the actions of Sammy Jankis rather than himself. The point of the entire movie is that memory is unreliable.
And, just to brag, since I have the limited edition DVD I get to watch the movie chronologically if I want. It is delightful.
I heard you can also watch it in order if you have a non-region 1 DVD. You can check out how through the site dvd.ign.com. It involves entering a code during a menu transition.
Look closely at Teddy's glasses at the beginning of the movie. They are laying lenses down. When the shot switches to the quick "reverse" shot, the glasses suddenly positions to be frames up.
Erm...actually my nit is backwards, but it's still a nit. The glasses start standing up, then are lenses down.
I was compiling the different fashions in which I could put this nitpick, but the fact of the matter is this: at the very end of the movie, during Leonard's "I have to believe that there is a world outside my own" soliloquy, there is a brief glimpse of Leonard's wife caressingly stroking his tattooed chest with the two of them on a bed. That patch of bare skin reserved "Maybe...for when I get him," as noted by Leonard in a previous scene with Natalie, has the words "I've done it!" tattooed in its place. It's a quick flash of a scene, but watch the denouement. I swear it's there, which leaves me asking, "Is this image Leonard's yearned reality?" In other words, is this a scene between him and his wife he WISHES to be true in lieu of what he had just done, what he has become, and...
SPOILER
...his wife's inadvertent death by his own hands?
Another point of interest: how does Leonard remember TO TAKE NOTES? This is something that occurred AFTER the accident. Otherwise, great flick.
He conditioned himself to take notes. Remember that throughout the movie he checks his pockets too, whether there's stuff in them or not. In his mind, the whole differentiation between him and Sammy is that he could condition himself to take notes and give himself tattoos.
Also, maybe he took notes on stuff before the injury?
I think the "I've Done It" tattoo is just Leonard's own mind telling him he's finally succeeded in killing his wife's murderer (though he only finds out about it, from Teddy). Something similar probably happened a year earlier when he really did kill John G.
Remember that Leonard also thought he was just pinching his wife, not giving her a shot. After all, as he himself says, memory isn't reliable.
(man it's been a while since I posted around here)
Anyway, just thought I'd mention that my theory on this movie has always been that Leonard really didn't have the condition he claims to have. I think it was more of a mental condition than a phsyical one. He allowed himself to believe these things because it was easier for him to live that way than to live with the fact that he probably killed his wife.
It's what makes the movie all the more tragic. The killing of Teddy is done because Leonard wants to keep a purpose for himself. A purpose where it isn't himself that is to blame for his wife's death, but one where he can constantly put the blame on others.
Clues to this are things like how he remembers to take notes, or how he remembers what the police told him after he died. The Sammy Jenkis story is one that he probably did experience, and used that as an escape for his mind. What really happened to his wife is pretty much impossible to say, but it's clear that Leonard has a much different condition than he's letting on.