In Pokémon Red and Blue, a Glitch Pokémon with a similar apperance as the commonly seen J Tetris block-shaped MissingNo. Unlike the usually harmless Missingno., 'M Block can cause more harm to the cartridge, but both of them can mess with the Hall of Fame data.
'M Block can be found in the same manner as Missingno. (see below), but when encountered it's name will consist of glitchy blocks, 'M, and some more glitchy blocks. Thus is why it's called 'M Block. It's also called 'M. When encountered, its cry will sound somewhat like a Cloyster's to a degree. Like Missingno., the screen will be black for about 2.99 seconds rather than 1.40 seconds with a
normal Pokémon and the Ghost, Kabutops, and Aerodactyl fossil Missingno.
To encounter 'M Block (or any member of the Missingno. family), make sure that you have a Pokémon that can use Surf and
Fly outside of battle (or a Pokémon that can learn both moves).
Fly to Viridian City and talk to the Old
Man who blocked the road near the beginning of the game. When he asks if you're in a hurry, tell him no, then
fly to Cinnabar Island. Go to the eastern (right) coast and begin to surf up and down that strip of land. On occasions, you might encounter Pokémon that were in the area that you were in before going to Viridian City. Also, you might encounter an unusally high-leveled (over 120) Pokémon that depends on your player's name. (As an example of this, KYLE will generate a lv. 152 Cloyster.) Once you encounter Missingno. or 'M Block, the screen will stay black just slightly longer (about 2.99 seconds) than usual. You will see what appears to be a glitchy J Tetris block (commonly described as a "backwards Tetris block") and a glitchy cry (either as a
short glitchy Nidoran male for Missingno. or a glitchy Cloyster for 'M Block). If 'M Block is at lv. 0, quickly catch it (if you desire to) with a strong ball (e.g. Ultra Ball). Once you catch it the first time (this goes for all Glitch Pokémon), it will become a Rhydon. Why? Rhydon is the first Pokémon on the hexedecimal chart, so it sounds like a logical choice for the game to do. After that, the battle will continue but nothing will be there for the opponent, so you could either catch it again (you will get a Ditto), or defeat it. On subsequent encounters, your 'M Block will not change its form, but you will still be battling against the "invisible Ditto".
An interesting ability the Glitch Pokémon have is increasing the quanity of the 6th item your holding to about 120. After 99, it will look somewhat like this {block}0 where {block} is a single tile from the game. Exploiting this is known as the Rare
Candy Trick because items such as the Rare Candy or Master Ball are used. It
may be a good idea to encounter a Missingno. and/or 'M Block (but not battle especially if Missingno.'s level is too high) with the Master Ball as your 6th item before catching it to make it easier.
Sometimes, you may or
may not find 'M Block or its not as easy to find as another Glitch Pokémon. That
may be due to your player name. If the 3rd, 5th, and/or 7th letter(s) in your name is M, it
may be easier to find 'M Block. In my case, I had no trouble finding 'M Block while using the name KYLE.
Please note that the only Glitch Pokémon you could encounter in Cinnabar Island with the "Coffee
Man trick" are Pixel Missingno. (most common form), 'M Block, Ghost Missingno. (looks like a Ghost Pokémon when you enter Lavander Tower without the Silph Scope), Kabutops Fossil Missingno. and Aerodactyl fossil Missingno. The other Glitch Pokémon could be found via GameShark or with the "Mew
Trick" but using a Pokémon with a Special rating at certain numbers instead of the Youngster with the lv. 17 Slowpoke.
