New Super Mario Bros. Cheats

Unlock Luigi:
Hold L + R and press A to select a saved game file to play as Luigi in single player mode.

Secret Challenge mode:
Finish the game. Start the cleared game file, then press Start to pause your game at the world map. Press L, R, L, R, X(2), Y(2). The message "Welcome to the Secret Challenge mode" will appear to confirm correct code entry. Similar to the original Super Mario Bros. for the NES, Secret Challenge mode will not let you backtrack in certain levels. To indicate whether a level has a Secret Challenge version, the new right arrow icon will be lit in the top right corner of the map screen.

Special background patterns:
When you load a saved game file that you have completed the game on, you will find a new blue Toad House at the beginning of World 1. Inside are four background patterns you can choose for the touch screen. You can purchase these with Star Coins. The fifth and final pattern can be purchased for 20 Star Coins when you have collected all star coins, complete all stages, and find all hidden exits.

Saved game icons:
A star will be added next to your saved game file when one of the following tasks are completed. Completing more than one will display an additional star. The tasks are to defeat the final Boss, complete all world maps by finishing all levels and locating all secret exits, and spending all Star Coins.

Unlimited Toad-House items:
When you load a saved game file that you have cleared every level, including the lettered bonus levels, Toad Houses will no longer disappear after you take the items. The only exception are the ones that appear based on your timer when you finish a level.

World 4:
Defeat the Boss in the last castle of World 2 as Mini Mario.

World 7:
Defeat the Boss in the last castle of World 5 as Mini Mario.

World 8:
Defeat the Boss in the last castle of World 6 as Mega Mario.

Mushroom house bonuses:
Complete a stage with a time having the last two digits of the same number to have a different color Mushroom house at the start of the World.

Have a time ending in 11, 22, or 33 for a red Mushroom house appears that awards items.

Have a time ending in 44, 55, or 66 on the timer for a green Mushroom house with a mini-game for an extra life.

Have a time ending in 77, 88, or 99 for an orange Mushroom house with a Mega Mushroom.

Control credits screen:
At the credits screen, use the touch screen to move the letters and hear sound effects from the game.

Extra lives:
Collect 100 Gold Coins to earn Mario an extra life.

At the end of a stage, jump up and land on top of the flagpole to earn an extra life.

Easy Blue Shell:
Go inside a red mushroom house. When Toadsworth makes the roulette block appear immediately dash to the end of the roulette block. Without stopping, jump at the end of it to get a Blue Shell. REMEMBER: This requires timing and practice.

World 1-1: Easy lives:
When you hit the "?" block containing the Mega Mario Mushroom, run as fast as possible to the end of the level and smash everything in sight. If you crash all the way through to the flagpole, you can earn up to five 1-Up Mushrooms and run your total number of lives up quickly.
User Cheat by ChrisGreasy

World 2-4: Easy lives:
There is a Koopa Troopa coming down the stairs at the end of the level. Stand on the block in front of the one the Troopa is on and jump up so that you jump on him. Do not press any buttons and let Mario continue to jump on him. After gaining the 1,000 points, you will start to get extra lives. Let it continue until you get the maximum number of 99 lives.

World 3: Get past electric balls as Mini Mario in Bowser's Castle:
First, use the middle green pipe to be shot up. Hold Up to climb and jump up until you reach the four electric balls that block your path. Go under the bottom one. You will soon be standing on top of a vertical wall. Hold X, run right, then perform Wall Kicks (face a direction and press A) all the way up the two walls until you can press Up to climb on the mesh again.

World 8: Defeating Baby Bowser and Boswer:
Before entering the castle, enter an orange mushroom house and keep the Mega Mushroom you receive. Enter the castle and do not use the mushroom until the boss Battle. As soon as you can move again, tap the mushroom and grab it. As Giant Mario, simply run into Baby and King Bowser and both will be defeated. You can get the satisfaction of revenge for all of the times in the past that you ran into them and died.
User Cheat by myalias

Avoiding Blockhopper:
On levels such as World 2-5, if a "?" box doesn't have a spinning "?", it is an enemy called a Blockhopper.

Dancing opponents:
Pay close attention to the monsters in any level. Notice that they will do some sort of dance or jump when the chorus in the background music sings. This does not include flying enemies, Bullet and Banzai Bills, and Bosses.

Giant Luigi:
Go to Toad Town dojo west and get a mushroom. Throw it at Luigi and he will become very big. Also if use on yourself, you will get bigger than Luigi and so on.

New Super Mario Bros. Official Website

New Super Mario Bros. Review - Gaming Age

New Super Mario Bros. Review - GameSpy

New Super Mario Bros. Review - IGN