The glitch dimension (as it is often referred to by fans) is a glitch in Gold and Silver Versions. Unlike some other glitches, this glitch is merely for altering the visuals of the game, and will not negatively affect or delete the saved file once it is executed.
Several different things can happen upon activating this glitch, one being that the game freezes upon activating it. The other is that the screen turns white with a small pink rectangle in the top right-hand corner and the game restarts with different colors. When activated, it alters the colors of everything from the area the player walks around in to the wild and Trainer battles. Also, it slows the processing speed when trying to view the player's party Pokémon when not in battle. Pitch black places like Dark Cave will be illuminated without the use of the move Flash. The Poké in Pokégear changes to ど◀ when the player enters their Pokémon selection. All fade-in and fade-out transitions are disabled.
Interestingly, the Ho-Oh on the title screen of Gold Version changes from a silhouette to a fully colored Pokémon.
Everything is completely white, except for the sprites (such as the player character, the NPCs, the Game Freak logo at the beginning). The sprites are either black, extremely darkened, dark blue, or near white. Sometimes an already-dark sprite will become white. Sprites with areas of high contrast (near black near white combinations) will appear partially black and partially white. Menus are not visible, but it is possible to navigate through them by memory. When viewing the PokéGear only the arrow selector pointing upwards is visible in the upper-left corner. During battles, the images of the Pokémon are not visible, but the blacked-out move graphics are. The specific cause of this is unknown, but is probably related to the cause of the Glitch Dimension.
When the game jumps to $E112, it starts executing data related to Pokémon cries as machine instructions. In particular, when Coin Case is used after hearing the Machop cry, the game will eventually reach address $E912. Data around that address is related to the overworld and can be manipulated through moving around in different patterns. When exiting Professor Elm's Laboratory and moving four steps to the right (prior to using the Coin Case after hearing the Machop's cry), the game will jump to address $FA98, which is in the middle of the data of the third Pokémon in the player's party. The game can therefore be made to execute specific code, based on the Pokémon's attributes such as species, item held, ..., by deliberately placing party Pokémon. By placing a specific species of Pokémon in the fourth slot of the party with the correct held item and first move, the game's execution may even be made to jump to the memory area that stores the items deposited in the player's PC, where code will execute based on the identifier and quantity of the items in the PC.
The glitch can be used for executing the code for the unused memorygame.
Then the player has to go back to Professor Elm's Laboratory, save the game, exit and moving four steps to the right. If you now hear the cry of a Bellsprout, it is possible to enter the memorygame by opening the Coin Case.