NEW CHEAT!
How to give mario power up's:
First, get all 121 stars, but don't see Yoshi! Start the game, and before mario say's "It's a me mario!" press A B L L R A, then select file 6, the game will be normal, just have mario walk over to the waterfall, and attempt jumping inside, and Mario will! It's a small room, with a sign and an original SMB block, the sign will read "You have found the secret area! And now you only have one last task, use the firey flower in the box above and defeat Giant Yoshi and you'll get a big suprise!"
Now, to trigger Giant Yoshi, you must unlock Toad using my other cheat, once you have Toad, talk to the Toad that's in the dungeon below the castle, when you arrive there, all the Toad's of the castle will be there, 5 total, each with a diffrent color dots and vest, they'll accuse you of leaving your post, and jump you, you'll duke it out with each toad around the castle, what you have to do is locate each toad and fire ball it from behind, watch out for Green toad's signature move, spores! Once you defeat all toad's, The Blue toad, will say "You may have destroyed my toad army, but you won't escape this!"
He will then do a little dance, the walls will rumble and your contoller will shake, use the cannon to blast onto the top of the castle, collect the lives and stuff (You'll need them!) Go to the area where yoshi should be, and he'll be huge! triple the size of bowser! And breating fire! then Mario will arrive to the scene, and tell you try to work together and destroy him, the strategy to beat him is to alternate characters by pressing the d-pad, first, use Toad to bombard him with fireballs, avoding the shockwaves, fire, and egg explosions, once he's down, switch to Mario, and grab him by the tail, and slam him into the castle tower! repeat until the tower collapses, and GY will fall to the moat, destroying the bridge, Toad and Mario will sigh in relief, but then Yoshi will growl and say "This battle isn't over yet!"
He'll jump out of the moat, and onto the grass, the Luigi will come, but his head explodes for some reason, now, GY will throw a giant egg towards the castle, have your characters jump off and slam onto the water, and leave Luigi to die, (He's still squirming around) Meanwhile, recover your health in the water, than jump onto the grass, and face GY in a last battle, what you have to do is avoid GY attacks, and wait for him to fire an egg, switch to toad and stop it in it' tracks by fireballing it, then carry it to the cannon, aim it at GY before he murders you, and fire! Repeat and you'll beat him! he'll combust into the air, and drop a bunch of boxes, in midair, the two heroes will jump around, joyfull, then walk back to the half broken castle, the bridge will be fixed somehow, then Peach will arrive and congrlagulate you, but she's worried about the castle, and how it's gonna be fixed, "don't worry!" Toad continued, " I have plenty of cash money! Good for fixing the castle!" the screen will turn black, good job, you did a special cheat!
Note: this wont work in SM64DS because the pause screen is diffrent)