Glitch City Laboratories Archives

In Pocket Monsters Blue, when you buy two sets of Ultra Ball x99 or Great Ball x99 it messes some data up.

If you bought two sets of Ultra Ball x99 the exit mat will no longer work, and if you save and reset you can see that what makes up the border has also changed.

If you bought two sets of Great Ball x99, your badges byte will be changed to something like 62h, which equates to having the Cascade Badge, Marsh Badge and Volcano Badge.

The cause is unknown. This glitch doesn't work on other versions, strangely not even in Red, Green or Pocket Monsters Pikachu.

Instead of another stack of x99, you can buy say 99 Great Balls and 1 Great Ball and get a different effect like no badges.

Do NOT save after buying the two sets of x99 Ultra Balls if you value your save file. You won't be able to escape Cinnabar Island PokéMart without blacking out, and there is no way to escape the Pokémon League at all, because loading the save file causes a freeze.

Relevant Poké Marts:

Lavender Town
Celadon Department Store - Great Ball section
Fuschia City
Cinnabar Island
Indigo Plateau

Copy and paste from my Youtube video:

Relevant Poké Marts:

Lavender Town
Celadon Department Store - Great Ball section
Fuschia City
Cinnabar Island
Indigo Plateau

So, we can essentially write arbitrary bytes in RAM (following those conditions, of course)? Could this be exploitable?

The glitch is present in all Japanese releases and English R/B. It does not work in English Yellow.

When adding an item to the inventory, the game runs through every single item in the bag, executing the following algorithm:

1. See if the currently checked item is the one that is added to the inventory
2. If so, try to increase its quantity instead of adding a new stack. If it fails, advance to the next item and go back to step 1
3. See if the item after the checked item is an end terminator (0xFF). If so, stop.
4. Advance to the next item and go back to step 1

It works great for most situations. Some of the people may have spotted the error already: Once the game tries to increase the quantity of an item, it does not bother checking for the end terminator anymore. Because of that, things may start to get pretty bad if there's a 99 stack in the last inventory slot. Let's see how it works out in action - say we have the following inventory:

[tt]Potion          x1
Ultra Ball      x99
END_TERMINATOR  x0[/tt]

I hypothesize that one could avoid this by buying enough items that the bag is almost full save for one FF.  Maybe. 

I find it somewhat interesting that the FF entries remain there after items have been added and removed, but I suppose there would be no legitimate reason to change them back to 00 if the method didn't have a bug.

I bought 30 master ball because D359(Player ID?) was 45(69)

[li]Why does the glitch work only in JP Blue, as well as international Red/Blue? Why doesn't it work as well in JP Red, or Green? (This intrigues me since they came out earlier than Blue.) What about the code is different in these games?[/li]
[li]It is possible to move items around with Pokémon Stadium and Pokémon Stadium 2. What happens if you use one of these games? Does moving a second stack of Great/Ultra Balls under a first one trigger the glitch? If you move several items at once from your pack to another location (either the GB cartridge's PC, the N64 cartridge's Color Case, another GB cartridge, or tossing the items), do these get replaced with FF bytes as they do on the Game Boy itself?[/li]