New Super Mario Bros. 2

Collect one million coins to unlock a title screen featuring a gold Mario and coins.

After getting 9,999,999 coins and maxing the coin counter, you get an alternate title screen with the mario statue now being a tanooki mario statue!

Complete the Castle level in World 1.

Reach "Triple Crown" status by getting 1,110 lives.

When you reach Triple Crown lives, (1110 lives), Mario will no longer wear his hat during gameplay.

Go to the first Star Coin then stand on top of the stairs. When the Noko Noko appears, go down to the second or third step. When the Noko Noko reaches you, jump (not stomp) on it. If done correctly the Noko Noko will bounce off the wall but Mario will keep jumping on it. Note: This will not work as Golden Mario.

To play as Luigi in the game's single player mode, you must first finish the game by beating Bowser in World 6. After you do that, when on the file select screen, hold down the L and R buttons while selecting a file with the A button. Luigi will now be your selected character.

Successfully complete the game. Then, highlight a saved game at the file selection screen hold L + R and press A.

Jump on the flagpole at the end of the indicated World when the last two digits of the timer displays the listed number. The original NES sound of a world being cleared, fireworks, and a rainbow will confirm success. Return to the world map, and an entrance to the corresponding rainbow level will appear at the entry point of each world.

World 1: Timer ends in "11"
World 2: Timer ends in "22"
World 3: Timer ends in "33"
World 4: Timer ends in "44"
World 5: Timer ends in "55"
World 6: Timer ends in "66"
Flower World : Timer ends in "88"
Mushroom World: Timer ends in "77"
Star World: Timer ends in "99"

Your save file can be adorned by as many as five stars, provided you meet the corresponding requirements (as indicated below).

Beat world 6
Gather all star coins in worlds 1-6, plus the Mushroom World and Flower World
Gather all moon coins in the Star World
Access all of the game's alternate paths (including those you must pay to unlock)
Obtain 1110 lives, which appears as three crowns

Don't use the golden leaf (which appears if you die within a stage too often) or you won't get to enjoy sparkling stars and that would be sad indeed.