For my first post on this blog, I’m going to start with a classic. MISSINGNO. I will be going over Yellow Missingno in another post.
For those of you who don’t know, Missingno. is a placeholder pokemon in the R/B/Y games, and ONLY the R/B/Y games. There ARE placeholder pokemon in future generations, but they are NOT Missingno. Please do not confuse them with Missingno.
Why is he called Missingno.? It stands for Missing Number. It’s not just a tranlsation thing, either. In the original japanese games, he is called KETSUBAN. While I cannot remember exactly what it means, Bulbapedia sources it as meaning Missing Number, just like in English.
In the R/B/Y games, the internal hex order of pokemon within the game are not in order of the Pokedex. For instance, The pokemon occupying Hex 01 is Rhydon, while 02 is Kengaskhan. Odd, isn’t it? Now, in R/B/Y, the last valid pokemon is at Decimal 190, hex BE. Now wait, you say! There are only 151 pokemon in Generation I! However, since this was the first pokemon game, there are a lot of beta elements within the final coding. Originally in Gen 1, there was to have been 190 pokemon. However, it was shortened down to 150, then 151 when Mew was added in last second. In place of those 39 extra pokemon slots, Missingno. was put in as a placeholder. Also, 3 of the Missingno hexes (B6, B7, B8) have the sprites of the Kabutops fossil, Aerodactyl fossil, and the unidentified Ghost pokemon. These Missingno have different mechanisms than the normal Missingno, which I’ll go into in another post. Another interesting factoid is that some of the Missingno. hexes actually have unused cries that supposedly were to be used by the unused pokemon. The rest just have an altered Nidoran cry with a Pitch and Length of 0. (more on this in another post.)
Because of his placeholder status, all his pointers for his stats point to 00 and he is specifically programmed not to learn any moves on level up. However, the rest of Missingno.’s data, from his sprite to his stats and TM/HM moves, are taken from his base stat pointer of 00, which underflows into hex FF, causing it to read data from the parties of Biker trainers. ‘M, being THE 00 pokemon, also takes the same data.
However, Missingno. only goes to 00 because he’s a placeholder pokemon and all his pointers are set to the same area ‘M is. That is why they are similar.
Now, when you encounter Missingno, whether it be from the Trainer Fly glitch or the Old Man glitch, your game pauses at the black screen much longer than most pokemon. During this black screen, Missingno. partially saves to your Hall of Fame data with junk. You can see this in action by playing R/B on Pokemon Stadium, where it states that the game is saving as you encounter him. According to Okk, Missingno. replaces the part of the save from lines 498-857 with junk data. This not only includes the Hall of Fame data, but also 256 more bytes of unknown usage beforehand. This is why your Hall of Fame is corrupted afterwards. Some say that avoiding catching Missingno. or ‘M will avoid this corruption, but the game saves as soon as you encounter him. (This includes when you send out your own Missingno. or ‘M.)
A common usage of Missingno. and ‘M is that they increase the number of items you have in the 6th slot of your bag. Specifically, he increases the number of items by 128, unless you already have more than 128 items in that slot. This is due to his encounter flag of Missingno., which is 0.
You see, when you encounter a pokemon, it sets it’s bit in the pokedex to seen. While 1-151 correspond to parts of the RAM in the pokedex, afterwards comes your inventory. Glitch pokemon with encounter flags between 249-255 and 0 set the 6th item’s quantity. It’s very complex on which bit it sets to on, but if you’re curious, you can look at the sources. Missingno.’s is 0, so it sets the bit that is usually 0 (if set, it would add 128.) Of course, this only makes sense if you know how binary works, and I’m not going to get into that here. Perhaps in another post?
And that’s all there is to Missingno. One of the most iconic glitch pokemon, if not THE MOST iconic, his peculiar traits can be explained by digging through the game a little.
Images taken from http://glitchcity.info/wiki/index.php/Old_Man_Trick and http://bulbapedia.bulbagarden.net/wiki/Missingno._(Pok%C3%A9mon)