Backup the Map0003.lmu file in your Yume Nikki folder.
Replace the Map0003.lmu file in your Yume Nikki folder with the one included in here.

Walk out to the balcony in the Real World.  You will be warped to the debug room.

What those things do:
Interact with the mirror to get the Fat Effect (text will be garbage)
Standing 8-bit Witch Madotsuki plays the 8-bit "equip effect" sound.
The Cat Face gives you all of the effects and warps you to White Desert B.  If you already have the effects, you get duplicates.
Flying 8-bit Witch Madotsuki starts the Witch's Flight event, but you can't move.
The chair in the top right corner lets you save, but...  you can't leave the chair.  And sometimes, the Witch's Flight event happens at the same time!
Go to the left of the traffic cone to warp to Mars-san's room.  Unfortunately, you are warped to a part of the map where you cannot move at all.

Notes:  
The sprites at the top of the screen are supposed to be cut off a bit.  
The background seems to mimic the balcony's.
Only Madotsuki's room in the Real World is modified, and only to warp to the debug room.  Because of this edit, you can no longer go out to the balcony in the Real World unless you use the original Map0003.lmu.
The debug menu is not enabled.  It can only be enabled if the game is started through RPG Maker 2003 (press F9).
