While in the park, press Up, Down, Left, Right, Circle, Right, Left, Down, Up, Circle(4), Start. If you entered the code correctly, you will hear a sound.
Get everything
While in the park, press Up, Down, Up, Down, Left, Up, Down, Up, Down, Right(8), Start. If you entered the code correctly, you will hear a sound.
Money trick
When your money is getting a bit low, just save the game, then re-load it. You will find that everyone of your visitors has left the park and within the space of about 5 minutes, at least 50 visitors come back and PAY to get in.
No money taken from bank
While in the park, press Left, Down, X, Circle(8), Start. If you entered the code correctly, you will hear a sound.