I had a related question that seems to be suitable for this thread.
I found a glitch where if I press up and down at the same time then walk down a set of stairs in this one room I can then jump threw a wall and warp to like level 8 or 7 dungeon.
Funny thing is when I warp and come out of the dungeon I'm in the dark world, but then if I use my mirror it changes from dark world to dark world then to light world.
I may post pics later.