Number of items underflow glitch (Generation I)
Posted by: Torchickens
Date: 2013-08-15 15:46:30
Trying to sell items in the PokéMart won't work when the number of items is 0 because you get the message "You don't have anything to sell.", however, if you have an inaccessible Fresh Water, a Saffron City gatekeeper will accept it and your number of items will underflow from 0 to 255.
This is a good alternative to using the ZZAZZ glitch or Super Glitch to corrupt your number of items. Here's a video so you don't have to skip to later in his run.
To get 255 items, you can do this:
Red/Blue:
*Prepare a Poké Ball in the sixth position then encounter Missingno/'M with the Old Man glitch to get 128 Pokéballs. Throw one of them to get 127, then throw a Master Ball to catch it. The quantity will change from 127 to 255. This works because #000's encounter flag is registered when you catch the Pokémon as well as seeing it. You can also encounter Missingno. /'M twice (just toss one of the 128 items to get 127 when the first battle ends)
Red/Blue/Yellow:
*Encounter a Missingno. with the Ditto glitch/Trainer-Fly variation that gives Missingno. such as losing to Misty's Starmie in Red/Blue (note Trainers in Yellow can have different Pokémon thus different Special stats). To avoid a likely freeze from Yellow Missingno. use a special stat of 182, 183 or 184 to encounter one of the 'special Missingno.' that don't freeze the game and use one of the two aforementioned methods under the Red/Blue section to get 255 of an item.