To unlock them, you'll need to do four things:
If your having trouble of doing all of those, buy Hint Movies at Peach's Castle (Located in World 1) to help you do all of these, or go to YouTube.com if your still having trouble.
Chat with our AI personalities
There is no purple bunny in the game.Some people claim that the purple bunny was a hint that Waluigi was going to be Super Mario 64 ds.
To unlock them, you'll need to do four things:Reach the normal goal in every level,Find all secret goals in levels which have them,Use all of the cannons the secret goals unlock,Collect all 231 Star Coins.If your having trouble of doing all of those, buy Hint Movies at Peach's Castle (Located in World 1) to help you do all of these, or go to Youtube.com if your still having trouble.
Some Hint Movies, including those for world 1-2 and 2-3, show a player hitting lots of enemies and gaining lives. I especially recommend world 2-3. Also in world 2-3, if you get the timing just right, you can jump on the Koopa Troopa on the stairs leading to the flag and keep jumping on it for as long as you like. (Until the timer runs out or you max out your lives.)
As you progress through the game you gain the ability to dig. Luigi will jump on Mario's head and Mario spins but instead of hovering he spins into the ground and you can move around but you can't see underground(hint: If you jump out of the spots that have an "x" if you come out of the ground in that spot you will receive a bean.)
I can just tell you one hint: Croco is weak against fire attacks. Get level 3 with both Mario and Mallow and try to always power-up magic attacks on both characters. When you battle Croco, use Mario's Fire Orb (or better flame attacks) on him. He'll get much damage. When somebody runs low on HP, use Mallow's HP Rain. If you do this, it will take about 3 turns to beat him! (for the first time at Bandit's Way) This also works for Croco battle in the Moleville Mines.