From Glitch City Laboratories
The Item Slot Duplication Glitch is a glitch which is only known to exist in the First Generation of the Pokémon games and allows the player to duplicate an item slot, allowing for over 255 of any item to be held. The most of an item that can be held with this glitch without the use of a game-altering device is 5100. It can also be used to change the "CANCEL" button to look like an item slot.
- The player requires 255 of an item in a slot below the first item (A way to do this is through to the Old Man Trick for when the player encounters a MissingNo. or 'M.)
- An item which is unimportant to the player in the slot directly below the item that the player has 255 of.
- Firstly, the player should toss, use, sell, or deposit in the PC all of the items in the slot below the slot with 255 of an item.
- The item slot with 255 will appear in the slot that was used for the lost item.
Items Acting as the Cancel Button
- Using the glitch once will make the last item in the player's inventory act as the Cancel button. Using the glitch twice will make the second to last item in your inventory act as the Cancel button, and so on.
- The player cannot scroll beyond the Cancel button, even though the scroll arrow is there.
- Items below the acting Cancel button will be unreachable.
- The acting Cancel button can be swapped with another item, which will act as the Cancel button.
Buying an item (or otherwise adding an item to the player's inventory) will erase the item acting as the Cancel button as well as those underneath it. A normally functioning Cancel button will be directly below the bought item.
- One can lose Key Items after performing this glitch.
- One can get rid of Key Items that they no longer need.
- The glitch allows for faster duplication of items than encountering a MissingNo. by means of the Old Man Glitch.