Nemo age 9: If you mix the mashed potatoes and sauce, you can't separate them later. It's forever. The smoke comes out of Daddy's cigarette, but it never goes back in. We cannot go back. That's why it's hard to choose. You have to make the right choice. As long as you don't choose, everything remains possible.
Nemo Nobody adult: There's no life without you.
Anna: Go slowly. I have to get used to it. I talked to you so much when you weren't there, it's strange for me to talk to you for real.
Nemo age 5: Why do we remember the past, but not the future? When you ask mommy, she says, stop asking why. It's complicated.
Nemo age 9: Why am I me and not somebody else?
Young journalist: Did Elise die or didn't she? I don't get it. You can't have had children and not have them.
Nemo age 9: In chess, it's called Zugzwang... when the only viable move.
Nemo Nobody aged 118: ...is not to move.
Nemo Nobody aged 118: It should be written on every schoolroom blackboard: life is a playground or nothing.
Nemo age 9: You have to make the right choice. As long as you don't choose, everything remains possible.
Young journalist: Everything you say is contradictory. You can't have been in one place and another at the same time. Of all those lives, which one is the right one?
Nemo Nobody aged 118: Each of these lives is the right one! Every path is the right path. Everything could have been anything else and it would have just as much meaning.
Anna age 15: You're the first and last person I'll ever love.
Nemo age 16: Ten days... That makes 14,400 minutes... I wish time would stop right now, that it would stay this way forever.
Anna age 15: They say if you slow your breathing, time slows down. The Hindus say so.
Nemo's Father: There was a card from your mother in the post. You haven't looked at it.
Nemo age 16: I know, I'll get to it.
Nemo's Father: Aren't you going to see her one day?
Nemo age 16: I haven't seen her for seven years. If she wanted to see me, she knows where to find me.
Nemo age 9: I can remember a long time ago. Long before my birth. I was waiting with those who were not yet born. When we're not born yet, we know everything. Everything that will happen. When it's your turn, the Angels of Oblivion place a finger on your mouth. "Shh..." It leaves a mark on the upper lip. It means that you have forgotten everything. But the angels missed me.
Nemo's Mother: You could've stayed with your father if you wanted to.
Nemo Nobody aged 118: Urgh, you're still here? Did I fall asleep? Sometimes I don't sleep so I think... I think about how it was... and all I have left. What do you see when you look at me? A grumpy old man who never answers questions? Who mixes everything up? Who's kept busy by getting his meals? That's not me. Me... I wear shorts. I'm nine years old. I can run faster than the train. I can't feel my aching back anymore. I'm fifteen. I'm fifteen and I'm in love.
Nemo Nobody aged 118: Daniel Jones.
Young journalist: Is that your name? Daniel Jones?
Nemo Nobody aged 118: Of course not.
Nemo Nobody adult: So... who has a joke? Anybody? I do! What's green, small and goes up and down?
Daughter: A pea in a elevator. It's not funny. Old people humour.
Nemo age 16: Sometimes I can see the future.
Anna age 15: Doesn't sound like it'd be much fun to know what's going to happen.
Nemo age 5: Daddy says you can predict exactly where Mars will be in the sky, even in a hundred years. But the funny thing is that daddy doesn't know what will happen to him ten minutes from now.
Nemo Nobody aged 118: Sometimes people call me Mr. Craft. C-R-A-F-T. Can't Remember A Fucking Thing.
Nemo age 16: I'm going to marry the first girl that dances with me tonight.
Answer: This film is mostly open up for interpretation but I understand it that young Nemo thought up older Nemo and it actually happened, maybe in an alternate universe. Don't forget that Nemo could remember the future so most of what he imagines is probably going to happen. Unfortunately he can't predict choice so he doesn't know which life happens so all of them happen at once and they don't happen as well because he chose to make no choice (Zugzwang). Hope that explained it.