2D Nightmare
2D Nightmare is the last of the three minigames which are exclusive to the Nintendo GameCube version of Rayman 3: Hoodlum Havoc. It is notable for the fact that the conditions under which it is meant to be unlocked were remain unknown.
Sometimes Rayman remembers being a kid, when everything was in 2D.—In-game description, Rayman 3: Hoodlum Havoc
2D Nightmare is a Rayman 1 flashback in the same style as 2D Madness. 2D Nightmare, however, takes place in Picture City, whereas 2D Madness takes place in the Dream Forest. Inspections of the files on the disc of the PC version of Rayman 3 confirmed 2D Nightmare's existence and name, and revealed that it had once been planned for inclusion in the other versions of the game, along with a chess minigame and a minigame in which the player controls a Xowar which is chasing Rayman. The existence of 2D Nightmare was further supported by the presence of a slot filled with question marks at the bottom of the minigame menu in Rayman 3. In 2003, a screenshot of the level was posted in an official RaymanZone gallery; when the forums were deleted, the image was lost and the minigame's existence was called into dispute. In November 2010, the screenshot was finally located.
Two other GameCube-exclusive Rayman 3 minigames exist. Mad Trax is a two-player kart-racing game, in which one player, controlling Rayman with the GameCube controller, races around an area in a similar fashion to the game's Crazy Shoe sections, collecting jewels, and the other player, controlling Globox, arranges the race-track by playing a Tetris-like game on the connected Game Boy Advance. The other minigame, Wheelis, is similar, but it involves four players; two controlling Rayman and Gumsi in giant shoes, and two playing the Tetris-like game on Game Boy Advances. Both Mad Trax and Wheelis have been unlocked successfully by connecting a Game Boy Advance playing Rayman 3 to a GameCube playing Rayman 3: Hoodlum Havoc.
In the GameCube version of Rayman 3, 2D Madness is unlocked simply by connecting a Game Boy Advance to the console. In the other console and PC versions of Rayman 3, it is unlocked by earning a certain number of points in-game. 2D Nightmare can reportedly be unlocked by connecting a 100%-complete GameCube version of Rayman 3 to a 100%-complete Game Boy Advance version of Rayman 3, but this method has not worked when attempted. Efforts to contact Ubisoft regarding 2D Nightmare were made, but produced no constructive responses.