On the title screen, press Down, Down, Up, Up, Left, Right, Left, Right, B, A. The words 'Monkey Ball' should change to 'Enable All' so that the screen says 'Super Enable All'.
Super Monkey Ball Jr. Hints, Tips, Tricks, Secrets, & Glitches
Unlock all the minigames. Then keep getting more
play points. When you get 2500 you can unlock
things such as golf course B and extra continue.
Keep unlocking things and eventually you will be
able to unlock Master mode. Master mode consists
of 5 levels that are extremely hard. My advice
is: be careful and don't give up!