There's no system of codes like that in the original Animal Crossing game for GameCube.
It's possible you're thinking of other features of the game like:
* Password Reset: You could use a password to reset your town to an earlier stage of development. This wasn't related to Tom Nook, though.
* The "Wishing Well": This lets you make wishes for items, but it's a random chance system, not a code-based one.
Let me know if you have any other questions about the original Animal Crossing! 😊