Glitches

Various glitches have been found in the game. Many of them were fixed for the release of Pokémon Yellow, and none of them exist in the third generation remakes, Pokémon FireRed and LeafGreen.

• 'M and MissingNo.: The two most famous glitches, occurring as a wild Pokémon encounter on Cinnabar Island or Seafoam coast after either talking to a certain man in Viridian City, or after trading with one of the traders in Cinnabar Island. Missingno is not a true Pokemon monster but a bug, its name means "Missing Number." The encounter is commonly exploited by players, as the glitch is known to duplicate items.^[1]
• Cinnabar Coast Pokémon: If the player surfs up and down the east coast of Cinnabar Island, Pokémon that normally appear from the last place visited will appear here (including Safari Zone Pokémon, which the glitch is most commonly utilized for). Also, many odd Pokémon over level 100 and trainers with glitch Pokémon have been found on the coasts of Cinnabar and Seafoam Islands (these can be found by performing the Missingno trick, and the kind of Pokémon, level of the Pokémon, and how many different Pokémon can possibly be found depend on the player's name).
• Item Duplication: A side effect of meeting both 'M and MissingNO. It causes the sixth item in the player's bag to increase by 128.^[1]
• "Mew Glitch": A glitch which, if properly performed, can trigger an encounter with a wild Pokémon of any species, most commonly utilized for Mew, a legitimate Pokémon normally available only through Nintendo promotional events.^[2]
• Other Glitch Pokémon: There are many glitch Pokémon that can be found in the game using a Gameshark or the "Mew Glitch". Usually they have unusual names (for example: 4. 4,TRAINERPOKE, etc.).
• Walk Through Walls glitch: One must perform the Glitch City glitch, but when the timer runs out, one must be in midair from jumping over a ledge. When sent back to the Safari Zone's main building, the Trainer can walk through walls inside the building. If all the player's Pokémon are poisoned and they faint, the Trainer is sent outside the building and can walk through walls throughout the Pokémon world.
• "Invisible PC Glitch": In Celadon City, there is a hotel, which has a layout extremely similar to that of a Pokémon Center. At the far right of the hotel, if the player presses the A button at the location where the PC in the Pokémon Centers usually are, a PC is somehow activated. This is generated by the creators copying the Pokémon Center map and making the PC invisible but not removing it completely.

• Pokemon Trade Glitch: When trading Pokémon between two gameboys, switching the power off at a certain point in the trade can cause one persons Pokémon to be replaced with the other persons. The other persons Pokémon should remain untraded, essentially copying it. this is often exploited for one person to get a strong pokemon while the other person does not have to give theirs up. It is also dangerous, as if done incorrectly one or both game files can become corrupted.^[3]
• Glitch City: An area like a town or city, composed of scrambled background graphics. Created by a series of steps involving the 'timer' in the Safari Zone.^[4]When a player uses their map in the Glitch City accessed through the Cinnabar Coast, it will say that they are in the Sea Route 20. However, Glitch City looks nothing like the Sea Route 20. In Glitch City graphics from different parts of the game are mixed up. The land and water can also be jumbled such that it appears that the player is standing on water or surfing on land. Further scambling of the graphics can be caused by pausing the game or certain other actions. If the whole city turns to water (which is sometimes possible), the player can keep surfing forever until the player gets stuck or the game automatically shuts off. There are several different Glitch Cities in the games, accessible via different methods, and detailed maps created of them show them to be fairly large.[3]

A good demonstration of many glitches is the tool-assisted speedrun of Pokémon Blue, which uses several glitches in order to beat the game faster.^[5]