There are three flavors to this glitch, two of which work on all versions except the original PlayStation version, and the third only works on updated (non-1998) PC ports.
On the Materia Exchange menu screen, the game will remember the cursor placement after exiting the menu. By placing the cursor on the final character, then losing a character for a story event, the cursor will be placed over an empty character slot. The game pulls from a garbage memory registry containing hexadecimal code which defaults to
00, meaning the empty character is believed to be equipped with the Buster Sword (two Materia slots) and a Bronze Bangle equipped with MP Plus Materia.
Free MP Plus Materia
At different occasions during the game, the party lose a character(s) who disappears from the Exchange menu. The instances are:
- First Gold Saucer visit (loses Barret)
- Post Temple of the Ancients (loses Aeris)
- Wutai sidequest (loses Yuffie)
- Jenova∙DEATH (loses the character who grabs the Black Materia)
- After the events at the North Crater–pre Mideel earthquake (loses Cloud)
- First Mideel visit (loses Tifa)
- Northern Cave split up (lose whichever team members go the other way)
By doing the setup at these points, then triggering the flag that removes the character, the garbage memory becomes active, and the two available MP Plus Materia can be moved out of the garbage memory and into actual memory.
Once the MP Plus Materia have been taken once, the slots are emptied. To refill the slots with MP Plus Materia the player must exit their save (close the entire application in the PC rereleases).
Smuggling Materia into Wutai
It is possible to use this to smuggle Materia into the Wutai sidequest by putting Materia from the player's inventory into the garbage memory slots in a prior instance, then retrieving them during the Wutai sidequest when Yuffie leaves the party. Since Yuffie steals Materia by priority, it is possible to 'protect' certain Materia for use.
If the player exits their save the Materia are deleted from that save file, and the empty slots will return to MP Plus Materia. In the PC rereleases the Materia persist upon exiting the save, but are lost if the application is closed.
Smuggling Materia across saves (PC rereleases)
Due to a bug in the coding, it is possible to use the glitch setup above to transfer Materia across save files. The player must initiate the glitch setup on a file, and get a Game Over. The player must load up a save with fewer characters than the one just used. The glitch will now be active on File 2, allowing one to place Materia into the garbage memory. However, the memory persists across saves. The player needs to place the desired Materia into slots one and two in the garbage memory, then get a Game Over. Finally, they must access a new save (with fewer characters than the cursor's position) and the glitch will be active again, having saved the Materia stored in the memory.
Since the game doesn't save progress upon Game Overs, it is possible to complete the process, remove the smuggled Materia from the active party, save, and then restart the cycle, to get multiple duplicated high-level Materia early in the game.