In most levels, there are multi-colored blocks held up by screws. With the white ones, you can drop behind the scenes to escape enemies or find secret exits by holding down on the d-pad for 5 seconds. In World 1-3 towards the end of the level, drop behind from on top the white block and run behind the black curtain. You will uncover a hidden mushroom house which contains a warp whistle.
Defeating Roto-Discs
To defeat a Roto-Disc you will need to be wearing a Tanooki Suit. After you have got a Tanooki Suit, find a Roto-Disc and make it so that it is underneath you. Right before it hits you quickly turn into the statue by holding the Down and B button. Once it hits from underneath you as a staue, the Roto-Disc will be defeated. Incase you don't no what a Roto-Disc is, it's the diso balllike enemy that rotates around a metal ball.
Defeating The Angry Sun
To defeat The Angry Sun, you must be wearing the Hammer Suit. Once you are wearing the Hammer Suit, throw a hammer at The Angry Sun and it will die.
Finding White Mushroom Houses
If you get enough coins in certain levels, you will find a White Mushroom House back on the map. Here are the minimum amount of coins you need to pick up at the following levels:
World 1, Level 4 -- 44 coins
World 2, Level 2 -- 30 coins
World 3, Level 8 -- 42 coins
World 4, Level 2 -- 22 coins
World 5, Level 5 -- 28 coins
World 6, Level 7 -- 78 coins
World 7, Level 2 -- 42 coins
The White Mushroom Houses in Worlds 1, 3, 5, and 7 give you P Wings, while the White Mushroom Houses in Worlds 2, 4, and 6 give you Anchors.
Infinite Lives in World e: Spike Fortress
This requires access to the e-Reader level "Spike Fortress". Near the third Ace Coin in the level is a pit of six Dry Bones. Jump on each of them in sequence while holding A for a boosted jump; by the time you knock down the last one the first few will be getting back up, allowing you to continue jumping in this way infinitely. If you manage to consistently jump on them until time runs out, you'll easily have farmed 150-200 lives.
Life Swapping
This trick is only done on Mario and Luigi Mode. To do this trick find a small m or l on the map screen, press the A button on it and start swapping lives using the controll pad. Then press the B button to get out.
Lots Of Lives
First go to level 1-2. Go about half-way through the level until there is a pirana plat by some coins in the air. Below the plat there are two bricks, smah the one with the P block and smash it. While the coins are bricks, run up and go to the right of the pirana plant. Jump and a 1-Up mushroom will pop up. Quickly grab the mushroom and go into the tunnel. When you come out of the tunnel, do this process over and over until time runs out and you will have a bunch of lives.
Magic whistle
On World One, Level One, get a red mushroom, and, if possible, a leaf (Just in case). Jump on top of the white platform. Hold down the down button until you drop behind the white platform. Then run, and don't stop even if you run into an enemy. You can jump if you need to. When you come to the black area, you will go behind it. You will go into a room, where you will see toad, and he will give you the magic whistle. This allows you to go to any of the next 3 worlds.
Many Tanooki Suits
In World 5 (Cloud World), the first available mushroom house has a Tanooki Suit. Get it and beat levels until you get to the cloud part of the world by beating the spiral tower. The game offers to save your game. Save it, then get game over. When you continue, you keep the Tanooki Suit you got at the mushroom house, and the mushroom house has returned! All of the other levels remain defeated as well, though the spiral tower remains standing, so you cna beat it and save your game, get game over, and get another Tanooki Suit each time! The suits make good replacements for leaves, mushrooms, and useless items (like music boxes) in your item list. Glitch only works for World 5 due to the ability to beat the spiral tower as many times as you want and save after each time.
No More Dry Bones
To make Dry Bones disappear, make him into a pile of bones and the walk across the screen until you can no longer see him. Then go back and he will be gone.
Secret Room In World 8-2
To find the secret room in world 8-2, go to the first sinking sand, go in it and let your self sink. When you at the bottom you will see your self in a secret room with two pipes. Both pipes lead to different rooms. After you get out of one of the pipes you just went in, you will end up near the end of the level.
Secret Warp Whistle In Fortress 1
To do this you need to have a Racoon Suit. Once you have the Racoon Suit, go near the end of the first room you appear in. At the end of the room, you should see a door and a Dry Bones. Quickly take out the Dry Bones and go near the door and run so you can fly until you can no longer go up. While you're in the air, keep going right until you end up in a room with a small chest holding a Warp Whistle. Once you have the Warp Whistle you will not have to fight Boom, Boom. (the boss of the fortress)
Selecting Worlds and Redoing Levels
Once you've deafeted Bowser, you can select your own world and redo the levels you've beaten in the past, but you can't redo fortesses and castles.
Special Suit Trick
Go to a mushroom house and pick a chest. If it contains a suit, get a game over. Now select continue. The levels you have beaten will not be reset, only the mushroom houses and the slot machine games. After continuing, go back to the same mushroom house where you've received the suit. No matter what chest you pick, you will always find a copy of the same suit. Repeat this trick to get as many suits as you want.
Special World Endings
Defeat the Koopaling at the end of an Airship (Worlds 1-7) while wearing either the Frog, Tanooki, or Hammer Bros. suit and receive a special message from the King.
Underwater Shortcut
There is an easy way to beat the ship level (after the tank level) in the final world. Just swim under below the ships. Keep pressing A so you won't sink too deep and die.
Unlock World Selection Screen
Beat the game clearing every single level (90 in total). Once Bowser is defeated, save and you will be brought to a World Selection screen where you can jump to any of the 8 worlds. All locked doors will have been unlocked and you can freely visit any stage/bonus stage/castle/etc.
Warp Flutes
Warp Flute 1: In world one, level three, go near the end of the level until you see a white block. Step onto this white block and duck, and after a while you will fall behind it. Stay behind the backround while going all the way to the end of the level.
Warp Flute 2: In world one's fortress, go to the area where the ceiling is open (it is just before a door with a skeleton koopa). Make sure you have a raccoon leaf. Fly up above the screen and then move to the end at the right. There should be a hidden doorway.
Warp Flute 3: In world two, go to the top right corner of the map. Use a hammer to break a boulder up there, and then continue to the right to find a hammer brother. Beat him to get the flute.
Warp to World 8
Once you've got two warp whistles you can use them both to instantly end up in World 8.