We have all played Pokemon at some part in our lives. Most of us remember the good old days, with red, blue, and yellow, and a rediculously hard pokemon league (hardest in the series). Still, those three games are greatly remembered for their glitches. There is the Mew Glitch (not under the truck silly; Google it), Glitch City, and the most famous of all Missingno. The Missingno is a double-sided coin, as killing it will give you 128 of the 6th item in your bag, but catching it will corrupt your save file, which has made many people nervous when researching with Missingno. There are a few theories why Missingno exists, some say it was so the developers could get through the game quicker (with land connecting Pallet and Cinnabar), others have come up with a theory that I think explains it better.

Let me explain the glitch first for those of you who don't know what to do. Please note that I am not responsible for any corrupted files and glitches that may occur from encountering Missingno, who may come up as 'M. First, make sure you have Fly and have been to Cinnabar Island. First, go to Viridian and talk to the old man who is to the west of the gym. When he asks you if you want to learn how to catch a pokemon, say yes, and watch. After he is done, fly to Cinnabar, and swim along the coast (half on land, half off). You should notice that you are encountering pokemon over level 100, and eventually you will find Missingno or 'M.

Here's how the glitch most likely works. There are room for 255 pokemon, but there are only 151 spaces taken up (yes, including Mew). When the old man shows you how to catch the pokemon, the game has to put your name into storage in one of the empty pokemon spaces so it says "OLD MAN caught Weedle" rather than "'your name' caught Weedle". When you leave the battle, you're still in a place without wild pokemon, so it keeps your name in that spot. The same goes for when you're in Cinnabar. When you swim on the coast, you're technically not in that route, but still in Cinnabar.

Now it gets technical. You see, for some reason, that area in Cinnabar never had any pokemon programmed into it, so your name takes the place of the pokemon that appear. Each letter in your name has a hexadomical value, letters 2,4, and 6 determining the levels, and 3,5, and 7 determining the pokemon that appear. To determine the level, take the numerical equivalent (A=1, B=2, etc.) and add 127 for uppercase and 159 for lowercase. For the actual pokemon that appears, check the chart at 'http://trsrockin.com/missingno4.html' to figure it out. Here is an example:

Name: MICHAEL

Levels: I= 9+127= 136, H=8+127= 135, E=5+127= 132

Pokemon: C= Golbat, A=Golduck, L= Cloyster

So there will be a level 136 Golbat, level 135 Golduck, and a level 132 Cloyster. A Missingno or 'M may still appear, so this method is flawed, but it does work quite well as to figuring out what pokemon will appear and at what level.

So hopefully this helps your understanding about Missingno a little more, and I didn't confuse you completely.

Information source: http://trsrockin.com/missingno4.html