28 P-Wings
Complete the game, then press Start at the ending screen. The next game will begin with 28 P-Wings per brother.
Always get three stars
At the end of most levels (in which you get a card). Use full speed with marios that allow you to run, and hit the bottom left hand corner of the "card block". If done right you will be able to get that star each time. MUST DO THIS EACH TIME AT END OF THAT LEVEL.
Avoid Damage From Bowser
When fighting Bowser in the final level of the game, his lower half will not do damage to you. That means you can avoid damage from his ground-pound attack by ducking if you have obtained a power-up at some point, or, if Small Mario, you can walk under him and through him without sustaining damage.
Beat Fortress via N-Spade
In the game, you need to wait until the N-Spade card game - which appears with every 80,000 points you earn - spawns and moves to the spot of a fortress on the overworld map. If you go there now and play it, the fortress will as if you had beaten it afterwards, being collapsed and unplayable. Note, however, that the bridges and locks affected by defeating the fortress normally will still not unlock or reappear, so only do this when these things are not required.
Change forms
Press Select while playing a normal game to change into different Marios or Luigis (Mushroom, Fire Flower, Super Leaf, Frog, Tannokie, and Hammer Brother).
Double Warp
Receive two whistles and use one to get to the warp room. In the warp room use the second whistle which will take you to the last part of the warp room. This will get you to level 8 to defeat king Koopa.
Getting the boot
Hold Y and press Select.
Hammer Suit
The hammer suit will make you invunderable to fire and you can kill ghosts with your hammers.
Random world
Wait until Mario and Luigi begin running around during the opening sequence. Press random buttons on the controller. The game will begin at a random world after the number of players are selected.
Usa Usa
Put in usausa in the game genie and more enemies will appear in weird spots. And also, the backround will be oddly colored.
Warp to Level 8
If you want to go straight to level 8, you must use a Warp Whistle to proceed to the Warp Zone, then use another warp whistle IN THE WARP ZONE. You will be transported to the level 8 pipe at the bottom of the screen.
Warp Whistle II
In world 2, after you beat Level 4, there is a stone right beside 4.Use the hammer and then there is a path that opens up.Fight the fire brothers and after you do that in the box is the Second Whistle.
Whistle Room
Go to world 1-3. Towards the end of the level, there should be a white rectangle floating in midair. Jump on it, then squat down. In a few seconds, you should fall through. Go to the end of the level. In a few seconds, you should see either Mario or Luigi { whichever Mario Brother you are } on a platform on the left side, and a Mushroom Person on the right. In the middle of the screen, there should be a box. Run to the box, and press B. A whistle should pop out. To use the whistle, you should be on the level select screen. Press B, and there at the bottom of the screen in a pink strip should be a whistle. Scroll over to it and press A. It will take you to a Warp Zone. Choose a world and press A. You can use your whistle in that game only.