List of Super Mario Land glitches
From the Super Mario Wiki
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This is a list of glitches in the game Super Mario Land.
NOTE: Unless otherwise noted, all names are conjectural.
Walk the Pipe
In any area with a Warp Pipe, Mario must dash to the top and swiftly press . Mario goes through the pipe, but he is shown walking as if as he did not.
One-Frame Small Mario
Death and Hit Mash-Up
Power-Up and Fire Mash-Up
Out of Bounds (Version 1.0 only)
In Chai Kingdom-3, Mario must press while being pushed off against the left side of the screen by a wall or object. If done correctly, Mario doesn't lose a life and reappears in the right side of the screen. If pushed by object while invincible, Mario is able to lose a life. 
At the end of a level, the player must scroll the screen, come back and scroll the screen again. This can cause platforms, enemies and even bosses to move out of bounds.
Superball and Yurarin Boo
Under the Pipe Travel
In a bonus room in Muda Kingdom-1, Mario must break the two Brick Blocks under the pipe and jump to the left side of the gap. If done correctly, Mario freezes in his jump pose and goes left, as if as he went through the pipe.
Untouchable Piranha Plant
Sometimes, if Mario jumps onto a Piranha Plant, he goes right through it without getting harmed.
If Mario jumps at a correct spot of a wall and jumps again, he can do a Wall Jump-like trick.