Play as Wario

Press L+R+X+Y+B+A while selecting a file and you will hear "Wario!!".

Unlock Classic Music: Complete world 1-1 in 15 seconds, includes star coins.

get mega for whole game

to get mega for the intire game. wjhat you have to do is die 100 times as mini mario. then when you go to a mega mushroom house you'll get a mega mushroom that is black with blue spots and toadsworth will say a specal message "master mario you have got a mega forever mushroom"
walk out and die. now die in a caslte becuase of no room.

Infinite Time in all Levels:

Use a Mega Mushroom and destroy every flagpole in the game(Including red ones) but not the bosses at the end of each tower/castle but the flagpole in the World 1 Tower as well. When you destroy the last one, 100 Fireworks will go off. It may take a while to finish. Then the timer will vanish.

Get a shot gun and shoot everything and make zombies your enemies.

hack into your game and type shotombies you wil get a resident evil kinda look game and you get hurbs to make and a crap loads of shot gun shells

Unlock sound test

At the title screen press A+B+L+R+START

If you type ABXYABXYRRLLRRLLRRLLABXYRLPOOPRRLXAB while singing Mary Had a Little Lamb into the microphone while using a mega mushroom while using Luigi while on level 1-3 while stomping ona Goomba after jumping through seven pipes consecutively, you will unlock MARIO PORN.

Unlock Sephiroth boss battle:

Pick up the blue shell 10 times in a row

You get to fight Sephiroth. But, being the overrated little douche that he is, he'll go down in 2 hits.

Beat the final boss as Luigi and unlock Yoshi code.

quote twilightprince

Unlock secret Challenge Mode:

At any world map, press pause, then press L R L R X X Y Y

Oh wait, that's a real code. My bad.

THIS REALLY IS A CODE!!! It makes the camera unable to turn back. Only to the right. It just doesn't go down or left. It makes an arrow appear. Are there any other secret codes?

Play as Bowser Jr.:

Beat the game on super challenge mode then at the end when it usually says...
"select file->L+R+A luigi"
it wil say...
"select file->L+R+x Bowser Jr."

Beat the final boss as shell mario (or luigi) and be able to play as a koopa!

Unlock a Resident Evil minigame in NSMB:

Beat the final castle without taking damage.

If you beat the game in 7 seconds, you can play as Bowser with a homing launcher and finally get rid of that nogood plumber.