Super Mario Bros. 3/Glitches

Note that the glitches here apply to the NES version, and unless noted have been fixed for later re-releases such as in Super Mario All-Stars or Super Mario Advance 4.

Airwalking
This is a simple and minor one. Go in quicksand with your P-Meter full as Raccoon or Tanooki Mario. Fly and instead of a flying sprite, Mario will have a walking sprite. This was not fixed in Super Mario All-Stars.

Brick Blocked
In World 3-6, there's a brick on one platform that contains a raccoon leaf. Throw the nearby koopa's shell at the block to release the power-up. Collect it. Then, quickly jump to the brick above and it won't break. This was not fixed in Super Mario All-Stars.

Gray Hammer Mario
Enter the bonus room in 7-8 which includes a Hammer Suit as Tanooki Mario. Jump at the giant ? block, then stand so that the bouncing suit hits you, but transform to a statue before it hits you. If you did it correctly, you should transform into gray Hammer Mario. You're completely invulnerable in this form - but you cannot enter the pipe to exit this room, so you're stuck until time runs out. Ths was not fixed in Super Mario All-Stars.

Invisible Muncher
In the second piranha plant level, enter with a P-Wing. Fly to the last thin pipe in the level and go on it. You'll get hurt and die for no reason at all!

Pipe bug
Go to either World 3-9 or World 7-5 as big Mario. Both have pipes directly beside ice blocks. Stand on the pipe and remove the bottom-right ice block from Mario's position, then run and duck to get inside (kick the ice blocks under you away as well). Once you're in this small gap, duck and jump to try to wedge yourself between the ice block and the pipe and hold down. If you did it correctly, Mario should eventually go down beside the pipe and land on the other side, except he's nowhere to be seen. You can now move the screen freely, but are stuck here indefinitely. You'll have to reset to get out of this.

Small to Fiery
In World 5-7, there is a wooden block with a fire flower. Release it as Super Mario but don't collect it. Next, get hit by a Pile Driver Micro-Goomba. After that, hit the question block directly to the left of the fire flower. Collect the flower and you'll become Fire Mario. Small Mario normally would become Super Mario. This was not fixed in Super Mario Sll-Stars.

Unfiery Bowser
Enter Bowser's Castle with a P-Wing. In the large room with the donut blocks, select the bottom path, and play all the way through until you land in Bowser's chamber. Here, fly all the way up and to the left to see a brick wall, fly over it then return back. Now drop back down to fight Bowser and he won't shoot any flames for the entire duration of the fight. This was not fixed in Super Mario All-Stars.

White Block Invinciblity
In World 5-7, go to the bonus area. Find the White Block and duck on it. After you fall behind the scenery, quickly exit the bonus area. If you were fast enough, you won't get hurt by any enemies!