Glitch Unown are invalid Unown in Pokémon Gold, Silver and Crystal that can only be found in Unown Mode of the Pokédex through glitching or hacking.
They cannot exist as usable Pokémon, because every set of DVs counts as a valid Unown letter.
Some variants of these glitch Pokémon have indecipherable sprites, kind of like glitch Pokémon from Generation I. Others such as the Gold/Silver:254 kind use a sprite that shows all Unown icons from A-Y in five columns, in a 'down, then next column' order. Other glitch Unowns are a combination of both of the possible appearances explained above.
Many of the glitch Unown cannot be seen as they either freeze the game, or reset it into a Glitch Dimension.
Glitch Unown are different between Gold/Silver and Crystal.
In Pokémon Crystal, at least the hex:FB glitch Unown has a sprite that looks like a corrupted version of another Pokémon's sprite (i.e. Noctowl for FB)
A notable glitch caused by a glitch Unown is Ilsty and ?. The game will switch to the evolution screen and act like a Pokémon named "Ilsty" is evolving into a Forretress, and then have a Graveler named "?" evolve into Golem.
Obtaining Glitch Unown
Glitch Unown can be obtained in Gold/Silver with the withdraw over 6 Pokémon glitch or through cheating.
Withdraw over 6 Pokémon method
Note: This has only been confirmed in Gold/Silver.
First prepare at least Pokémon five boxed Pokémon, and a full party with the fifth party Pokémon having a Defense modulo 256 byte (DB13) of your choice. Both the party Pokémon and the boxed Pokémon should be nonvaluable.
The value from DB13 will be written to the first Unown in the UnownDex, but the player's Pokédex seen and own addresses will be corrupted, causing the player to end up with different Pokédex in the Pokédex, so a player should not do this glitch if they have a complete Pokédex and don't want to lose it.
The GameShark code 01xx24DC (Pokémon Gold/Silver) or 01xxD9DE (Pokémon Crystal) will replace the first Unown in the Pokédex's Unown Mode.
Gallery (Pokémon Gold and Silver)
A glitch Unown with a blank appearance and a hexadecimal identifier of FD (dec:253).
A glitch Unown with a sprite that shows all Unown icons from A-Y in five columns, in a 'down, then next column' order. Hexadecimal identifier FE (dec: 254).
Some of the glitch Unown look kind of like certain glitch Pokémon in Red, Blue and Yellow. This glitch Unown has a hexadecimal identifier of FC (dec: 252).
Some of the glitch Unown look similar to both Unown with a hexadecimal identifier of hex:FD (dec: 253) and hex:FC (dec: 252).
Gallery (Pokémon Crystal)
A glitch Unown with a blank appearance in Pokémon Crystal. It has a hexadecimal identifier of FF (dec: 255)
This glitch Unown has a hexadecimal identifier of FE (dec:254). Black and white vertical 'pipes' can be seen.
A glitch Unown with a hexadecimal identifier of FC (dec:252). Black and white vertical 'pipes' can be seen like FE (dec:254) but the overall shape is centered and like a square.
A glitch Unown with a Hexadecimal Identifier of FB (dec:251). It incorporates parts of Noctowl's sprite.
- Ilsty and ?