From Bulbapedia, the community-driven Pokémon encyclopedia.
A glitch Pokémon is a Pokémon that only exists in the games due to programming oversights, when the game attempts to gather data for an invalid Pokémon.
Some glitch Pokémon have characteristics derived from the game's default error handling capabilities for an invalid Pokémon, such as "Missingno." or "??????????". Another example of this is the learn-set data for a Generation IV Egg, where it learns Splash as a starting move, likely to prevent the game from crashing due to an invalid move being used.
In Generation I, some glitch Pokémon may freeze the game if sent out on the opponent's side, depending on their Pokédex number and the version used, and glitch Pokémon with index numbers greater than 199 will always bring up equivalent glitch Trainers if encountered directly in the wild. These glitch Pokémon cannot be obtained via a wild battle, and must be obtained using a different glitch to the Ditto glitch or old man glitch, such as evolution from another glitch Pokémon, trading an equivalent index number glitch Pokémon to another version, or by executing the Johto guard glitch.
Additionally, catching certain obtainable glitch Pokémon in Generation I may cause endless Pokédex data to appear. To avoid this, the player must have activated a specific flag, if this is a hybrid glitch Pokémon, the flag is activated by either seeing a specific Pokémon or owning a specific Pokémon. Specific glitches (like the Super Glitch move or the ZZAZZ glitch) may cause the saved file to be corrupted or erased.
- Main article: List of glitch Pokémon
- There are 39 Missingno. with identifiers in between real Pokémon, which would add up to 190 Pokémon.
- Shigeki Morimoto confirmed that there were once 190 Pokémon planned for development in Pokémon Red and Green. The error handler Missingno. is used for blank or erased Pokémon data, and most of its characteristics are either a translated 0 value (e.g. default Nidoran♂ cry with pitch 0), or blank data rolled over to the next logical values (e.g. base stats denoting the rosters of several Burglars).
- The reason for the large amount of glitch Pokémon in Generation I is because only 151 values correspond to valid Pokémon, while Pokémon species index numbers are stored in 8 bits allowing for up to 256 values. This leaves 105 values not corresponding to a valid Pokémon; excluding the 39 Missingno. leaves 66 different values for other glitch Pokémon.
- In Generation I, a large number (43) of glitch Pokémon have the small katakana character ゥ u in their names. It is unknown as to why this specific katakana character appears so often.
- The only other Japanese character that appears somewhat frequently in glitch Pokémon's names is small ァ a. The hiragana ぉ o and ぇ e also appear, but less often.
- The reason for any Japanese text in an English game can be seen here.
- In Generation I, most glitch Pokémon have 4 in their names, like 4 4 Hy.
- 23' 0"/880.6 lbs. are the most common height and weight values for Red and Blue glitch Pokémon, and 23' 2"/1031.6 lbs. for Yellow. It is unknown as to why any glitch Pokémon have the same values, however.
- Some Glitch Pokémon have four or more evolutionary stages.
- Encountering a Missingno. or most other glitch Pokémon will cause the screen to go blank for a delayed amount of time before the battle begins.
- ↑ Smogon Forums