Leonard Shelby: I have to believe in a world outside my own mind. I have to believe that my actions still have meaning, even if I can't remember them. I have to believe that when my eyes are closed, the world's still there. Do I believe the world's still there? Is it still out there?. Yeah. We all need mirrors to remind ourselves who we are. I'm no different.
Natalie: Is that what your little note says? It must be hard living your life off a couple of scraps of paper. You mix your laundry list with your grocery list you'll end up eating your underwear for breakfast.
Leonard Shelby: Facts, not memories. That's how you investigate. I know, it's what I used to do.
Leonard Shelby: Memory can change the shape of a room; it can change the color of a car. And memories can be distorted. They're just an interpretation, they're not a record, and they're irrelevant if you have the facts.
Teddy: You're not a killer. That's why you're so good at it.
Leonard Shelby: I meet Sammy through work. Insurance. I was an investigator. I'd investigate the claims to see which ones were phony. I had to see through people's bullshit. It was useful experience, 'cause now it's my life.
Leonard Shelby: Now... Where was I?
Leonard Shelby: You know, I can remember so much. The feel of the world... Her. She's gone. And the present is trivia, which I scribble down as fucking notes.
Teddy: So you lie to yourself to be happy. There's nothing wrong with that. We all do it.
Natalie: You sad, sad freak. I can say whatever the fuck I want, and you won't remember. We'll still be best friends. Or maybe even lovers.
Teddy: You know, I've had more rewarding friendships than this one. Although I do get to keep telling the same jokes.
Answer: The are no alternative endings for this film, all that is on the third disk is the movie played in chronologial order so you can see how things really panned out.