List of Wario Land 4 glitches
From the Super Mario Wiki
This is a list of glitches in the game Wario Land 4.
To perform the Vertical Zipping glitch, the player must get into a corner which is four blocks high. They then must go right next to the wall, and turn around so they face away from the wall. The player must jump, and just before Wario hits the ceiling, the player should press down and forward for a split second, then hold forward. To zip, the player must rapidly press while holding either left or right.
When Wario picks up an object, there is a slight chance that when the object leaves his hand (whether he throws it or drops it), something may still be in his hand, even if nothing appears to be there. Wario must throw the Invisible Object in order to get rid of it.
Walk Through Walls
The Walk Through Walls glitch may be difficult to successfully perform. If the player jumps repeatedly against a wall of blocks, they may be able to walk through them. However, Wario may become stuck inside the wall.