PP underflow glitch (disambiguation)

Miscellaneous glitches of Pokémon Red and Blue and Pokémon Yellow

Amazing Man (Red and Blue only) | Cable Club escape glitch | Celadon looping map trick | Champion Blue music muting glitch | Coastal Flooding | Confusion and Substitute glitch | Cooltrainer move | Cycling based glitch maps | Escape sprite handling glitch | Evolve without an evolutionary stone (Red and Blue only) | Evolving Raichu (Red and Blue only) | Expanded item pack | Expanded Pokédex | Focus Energy glitch | Get stuck in a wall | Ghost Bicycle glitch | Glitch encounter system | Glitch City RAM Manipulation | Infinite Blaine Door | Introduction Nidorino glitch (Red and Blue only) | Invisible PCs (Red and Blue only) | Invisible tree glitch | Item stack duplication glitch | Mute the music in the Pokémon League | Partial trapping move link battle glitch | Pokémon Tower Pokédex glitch | PP underflow glitches | Recovery move glitch | Rival's effect | See a Ghost without a Silph Scope | Selfdestruct and Substitute glitch | Silph Co. PC Glitch | Slot machine glitch | Stand on a tree | Statue behavior glitch (Red and Blue only) | Super effective move AI flaw (Red and Blue only) | Super Glitch | Surf down glitch | Swift miss glitch | Transform assumption glitch | Transform Empty Move Glitch | Trick Zone | Vending machine purchase glitch | Walk around with only fainted Pokémon (Red and Blue only) | Walking lag glitch | Walk on water through Surf | Walking Pikachu happiness glitch (Yellow only) | Wild appeared! | ZZAZZ Glitch

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The PP Reset Glitch is a glitch in the Generation I Pokémon games. It allows certain Pokémon to have one of their moves' PP underflow to large values after reaching zero.

Moves that cause an auto-select

This glitch functions by abusing the auto-selection of moves caused by certain moves. The moves that cause this are the following:

• Bind
• Clamp
• Fire Spin
• Hyper Beam
• Metronome
• Mimic
• Wrap

While these moves are not absolutely necessary for the glitch, it will make performing it considerably easier.

Requirements

• A Pokémon to use for the glitch, preferably knowing any of the moves listed above. If the Pokémon used does not know any of these moves, it will have to be frozen and defrosted, which requires the opponent to either use a Fire-type move or Haze (Pokémon cannot thaw out on their own in Generation I.)

Procedure

1. Make sure the move that will be used for the glitch is at 1 PP, or a slightly higher number for the trapping moves.
2. If the Pokémon used does not know any of the moves listed above, have it become frozen.
3. Perform the move. If a frozen Pokémon is used, it will have to thaw out when the move is used for the glitch to occur.

The move's PP will now become 63, regardless of whether PP Ups had been used on the move.

How it works

The reason this glitch occurs is that in Generation I, there was no check to prevent a move's usage after an auto-select with 0 PP. This was first added in Generation II.

The amount of PP given to the move after it underflows is determined by the amount of PP Ups that were used on the move. In Generation I, the PP of moves was stored in one byte, in which the first two bits stored the amount of PP Ups used on any move, and the last six stored the amount of remaining PP. So, when a move with 0 PP is used, its value resets to 255, giving the move 63 PP. This value is higher than any attainable without this glitch, as moves in Generations I and II with 40 base PP maxed out at 61, likely due to a lack of data space. If no PP Ups were previously used on the move, the maximum amount will be applied. If PP Ups were previously used on the move, the move will lose one PP Up.