Avatar: The Last Airbender, Book 1: Water

Koh:
It's been a long time since I've added a child's face to my collection. So, how may I help you?

Aang:
I need to find the moon and the ocean.

Koh:
Their spirit names are Tui and La - "push" and "pull". And that has been the nature of their relationship for all time.

Aang:
Please, help me find them. An entire culture could be destroyed if I don't get their help.

Koh:
Oh, you think you need their help? Actually, it's quite the other way round... SOMEONE'S GOING TO KILL THEM!

Aang:
What do you mean? How can I find them and protect them?

Koh:
You've already met them, actually. Tui and La, your moon and ocean, have always circled each other in an eternal dance. They balance each other. Push and Pull. Life and Death. Good and Evil. Yin and Yang.

Aang:
(remembering the fish in the Spirit Oasis) The Koi Fish! (Koh spins back to Aang, who quickly wipes the excitement off his face) I must be going now.

Koh:
We'll meet again...