(Please don't call them Pokegods!)

This cheat is for Pokemon R/B/Y

Although 'M and MissingNo (in any of his four forms) can appear by doing the Coffee Man trick, there are other Glitch Pokemon that will only appear by using the Mew Glitch or a GameShark code. Sometimes these Pokemon are known as "PokeGods", but they are really just glitches like 'M and MissingNo - not super-powered Pokemon or G/S/C Pokemon obtainable in R/B. Most (if not all) of these Glitches are untrainable - since their number is so high, they revert back to Rhydons (HEX value 01) when caught. However, if you catch them twice, you can supposedly train them. Some of these Glitch Pokemon learn glitched moves, as well. Sometimes you will see nicknames given to these glitches like Anthrax or Beepin - they are still just glitches like 'M and MissingNo.

Some people claim that these are fragments of removed Pokemon, but they are most likely just glitches. There is no way to catch Marill, Ho-oh, Togepi, or any other G/S/C Pokemon in the original R/B versions. These Pokemon are not programmed into these games, so there is no way to catch, view, or train any G/S/C Pokemon in R/B/Y - they also don't appear in Hall of Fame screens. Any codes that explain how to get G/S/C or Advanced Generation Pokemon in R/B/Y are fake - end of story.
Several fake Pokemon are also rumored to be accessible in R/B as "PokeGods". A well-known example of this is Venustoise. Anime fans will remember the episode, "The Ghost of Maiden's Peak", in which a wayward Gastly battles against Ash and Team Rocket after trying to take James and Brock. This Gastly uses various unconventional methods of attack against the Pokemon - for example, it chases Pikachu with a giant mousetrap, and chases Charmander with a fire extinguisher. To battle Squirtle and Bulbasaur, it produces their most evolved forms and merges them together (named "Venustoise"). Many people online offered elaborate fake methods of obtaining this Pokemon in the games. Other fake Pokemon called "PokeGods" include Charcolt, Charzilla, Pikaflare, Pikablu, Pikared, Flareth, Vulcounare, and Kuravaiya. Basically, if you see a R/B/Y code to get a Pokemon not included in the original 151, the code is false (unless the "Pokemon" is actually a nicknamed glitch).