At the character selection screen, hold L1 or R1 and select a character.
Easier Putt in Minigolf
While putting in the minigolf course, hold down the walk button and the aiming line will move a lot slower and make it easier to aim.
Expert difficulty level
Beat "Challenge" mode on the hard difficulty level.
Play as T-Rex
Beat "Challenge" mode on the hard difficulty level with the Elephant.
Secret options
Beat "Challenge" mode on the easy difficulty level to unlock a secret option to make people small. Beat "Challenge" mode on the medium difficulty level to unlock a secret option for more speed.
Alternate character appearance...