The FC world (short for Famicom, the Japanese counterpart to the NES) is an area where the game's graphics change to resemble a 8-bit RPG. They contain both overworld areas and dungeons that are considered to be an homage to the game Mother. In the FC worlds the menu no longer fills the screen.
In some English translations of Yume Nikki, the game may crash when entering an FC world with all effects due to a misnamed file. To fix this, rename FCM2ALL.xyz in the folder "Picture" to FCM２ALL.xyz (with the superscript "２" character).
The FC house is accessed from the Static Maze in the Shield-folk World. The Demon effect can be found inside it. Staircases going up and right lead to a boss fight of sorts, as well as a dead end located in FC world A.
FC World A can be accessed by talking to the creature in the Mall section of the Dense Woods. By solving the Teleport Maze, you will end up in a Wilderness area with a box that takes you to this FC world. This section of the World contains one house that takes you to an underground complex which called FC Dungeon that connects to the White Desert B. This dungeon contains the Glitch event.
FC World B is accessed by talking to a certain Pirori, randomly selected each dream, in the Barracks Settlement. It contains a house with the Buyo Buyo effect inside. There's also a location with 6 pyramids with a FC Demon inside. He will teleport you to the FC house.
FC World C is unreachable without cheating; and refers to the large, inaccessible chain of islands to the west of the main FC worlds.
(More Maps coming soon)