This is a list of glitches found in Doki Doki Panic, Super Mario Bros. 2, Super Mario All-Stars' version of Super Mario Bros. 2, and Super Mario Advance.
Super Mario Bros. 2 glitches
Battle Birdo again
In World 1-1 or 2-1, if the player defeats Birdo, they must go to the Hawkmouth, but not go in, and come back to where Birdo was fought. She comes back when the player returns, and the crystal ball that Birdo dropped will still be there along with her. When she is defeated, she doesn't drop another crystal ball. She cannot be fought again. This glitch has been known to work in the NES and Super Mario All-Stars versions.
Bob-omb Ambush
If the player throws a POW Block and then immediately picks a patch of grass where a Bob-omb is hiding, the Bob-omb appears to die and fall off the screen. However, the next time the player enters a new area, such as going through a door, climbing a vine, or dying and restarting the level, the Bob-omb will reappear and explode, sometimes causing damage to the player.
Bob-omb Block
This glitch will work on any version of the game. Go to World 5-3 and go to the vase spawning Bob-ombs. Throw a Mushroom Block so that it's two blocks left from the vase. Next, wait for the vase to blow up. Now throw the Mushroom Block where the vase was, then go left to scroll the block off screen. When you go back to it, the Mushroom Block will be spawning Bob-ombs.
Bouncing Key
This glitch can happen in World 1-3. First, the player must enter the last door in the stage. Then, the player need to enter the door that has the Key with a couple of Phantos, pick up the key, and exit the door. The player needs to fall down to the space where there are Mushroom Blocks. When in the middle of passing by the Chains, the player must throw the key onto a wall, and it will look like that it's going to land on the player. If its done correctly, the key will bounce on the head of the player. If the player defeats a Spark with the bouncing key, there is an 85% chance of getting a heart.
This glitch can also happen in the Game Boy Advance version and the All-Stars version.
Climb Above the Screen
When climbing upwards very fast (with the fast climb glitch) at an area change point, the player can get above the screen without going to the new area. This allows fast access to other areas in some levels, such as World 7-2, where the player cannot get above the screen via other methods (due to lack of openings).
Climb Over a Vine
In any level with a Hoopster, the player can climb to the top of a vine and continue to hold up. If a Hoopster happens to come up to the top of the vine and push the character up while the player is still holding up on the controller, the character will be in the climbing animation a few feet above the vine. The character will fall as soon as the player lets go of the up control.
This also works in the Super Mario All-Stars and Super Mario Advance versions.
Climb Very Fast
The player can climb climbable objects very fast by simultaneously holding both up and down. This usually isn't possible in a standard controller, but easy to do with a modified controller. It can also be done via Virtual Console, as the Wii Classic Controller and Gamecube Controller have both a Control Stick and D-Pad, which both serve the same function in NES and SNES Virtual Console games.
Crystal Demise
Occasionally in World 4-1 on the NES version, when the player grabs the Crystal at the end of the level, the Hawkmouth disappears and the players fall to their doom through the floor.
Death by Potion
If the player throws a Potion above the screen, and then goes through the door, they appear in Subspace at the bottom of the screen and instantly die.
Defeating Birdo with a Key
This can be done in level 1-2 of the game, in all versions. After players get the key, they must then do a Super Jump off of a Ninji, and then they will find the door to the Birdo battle. Players can go into the door with the key, unlike Mushroom Blocks, enemies and vegetables. They can defeat Birdo with 3 hits with the key, although Phanto is still there to attack them.
Die and throw a vegetable at the same time
The player must have one heart left. He or she must pick up a vegetable and get touched by an enemy at the same time. If done, the vegetable will be thrown and the enemy will get hit by it.
Disappearing Mushroom Blocks
If the player throws a Mushroom Block offscreen and does not see it land, even to a place where it should safely land, it will disappear until the player leaves through a door and comes back.