Unlock Mario
Beat Goomboss behind 8-star Door in the rec room.
100% success rate. 

Unlock Wario
With Luigi in mirror room, hop into Wario's painting and beat the Giant Ice Bully.
100% success rate. 

Recover Health
When you want to recover health, find a body of water and swim under. Then, simply swim back up so your characters head is out on the surface. Your health will be replenished.
100% success rate. 

Stop the clock
If you jump into the tick tock clock level entrance when the minute hand is on '12' everything in the level (minus enemies) will be stopped as if time stopped.
Submitted by 0nemesis0. 100% success rate. 

Unlock Luigi
Beat King Boo in Luigi's Painting on the 3rd Floor of Big Boo's Haunt.
88% success rate. 

Have fun with the Goomboss
If you go back to the place behind the Princess's Drawers to the door with an 8 on it with Mario and enter the fight with Goomboss, he will eventually throw a mushroom. Touch the mushroom and Mario will grow tall, just like in the classic Mario games.
Submitted by 0nemesis0. 

Mario loses his hat
Go to the level where you can see the snow level in the mirror. Climb the mountain until you get to the head where the penguin is found. The snow head guy will blow you off. If you are Mario, Luigi, or Wario, your hat will fall off and you can leave the level without it.
Submitted by 0nemesis0. 

Go to: Super Mario 64 DS Info Page | nGaming Home Page.