Bonus Ending
After the rather unusual manner in which Mother 3's creators opted to end the game, the bemused player is left with nothing more than a blank screen with text reading "End?". Wish as one might, this black screen will last until the power is cut.
Fortunately, there is still a bit more to do: Using the control pad, you can actually move the "End?" text around (note that the controls are reversed, so up is down and down is up) and press the "A Button" to initiate conversations. Continue to move around and "talk" until the game's credits begin (and "yes", it will take a LOT of talking).
Glitch: New Bonus Game
If you beat the game in File 1 with all PSI, copy it to File 2. Now, start a new game and save over File 2. Lucas and Kumatora will have every PSI to start with. Lucas won't be able to use it until he gets the ability to, but then it will work.
Unlock Hard Mode
Enter your name as HARD MODE at the Shrine in Chapter 1 to unlock Hard Mode. The enemies have a lot more life and there are other little changes to make it harder.