New Super Mario Bros./Cheats

Instant transport
For the above tips, you can take a Mini Mushroom in reserve.
 * World 4: Defeat the boss in the castle of world 2 as Mini Mario.
 * World 7: Defeat the boss in the castle of world 5 as Mini Mario.

One strategy is to switch to Mini Mario in the boss room before fighting the boss. Another strategy is to fight the boss as Fire Mario but switch to Mini Mario for the last hit. To damage the boss as Mini Mario, you need to ground pound; jump then press. Having defeated the boss, Mini Mario will fall through a small gap and flip a sign indicating the next world. There is no way to summon a reserve item after the boss is dead.

Play as Luigi
At the "Select A File" screen, hold L + R and press A to play as Luigi.

Coin block
The number of coins you get from a coin block depends on the time between your first hit from the block and your second hit etc., so if you ground pound a coin block from above as Super Mario and keep pressing, you can get the maximum number of coins(14) and a super mushroom. You cannot stop or you won't get a super mushroom. You can also do this within a tight space between the platform you are standing on and the coin block and hit it at a regular interval.

Unlock Challenge Mode
To enable challenge mode, which prevents the screen from scrolling back where you came from, just like the original Super Mario Bros., press on the map screen. From there, press. Enter the same code to disable challenge mode.

Toad Houses
If you need additional Toad Houses, you can make them. You need to clear a course by touching the flagpole when the last two digits are a certain value. (You can also do this in towers and castles if you kill the boss at the correct time, but this is more difficult.) You can do this in any level, even 1-1. If the timer ends in: The house will appear at the beginning of the world. (You do not need any Star Coins to reach it!) If there is already a house there, then you need to clear it before you can make another one. If you want, you could make a house in each world and then save the game. If you have trouble with the timer, then go stand next to the flag pole, and make a small hop onto the bottom of the flagpole at the correct time.
 * 11, 22, or 33: A red house appears.
 * 44, 55, or 66: A green house appears.
 * 77, 88, or 99: A mega house appears.

99 lives
Go to World 2-4 and go to the part where you need to jump on top of the "?" button (near the end of the level). Kill everything except the green turtle that is coming down the stairs. Don't use the fireballs at the green turtle or else it won't come back unless you die or re-do the level. Jump on top when it lands on the 3rd step from the bottom.

If you did it correctly then all you got to do is wait until you get 99 lives. If it didn't then try again. It's better if you have the fire power and a extra one just in case you die (or else you need to start all over again). This is good if you are low on life and hate redoing the level.

Easier 99 lives
Why jump on a shell when a shell can collect the 1UPs for you? On World 7-5, drop a Koopa shell between the rotating Bullet Bill cannons shown in this video. The shell will kill the Bullet Bills for big points, earning you a 1UP about every four seconds. When you're finished simply run to the flagpole to finish the level before time runs out.