Pomeg glitch

Miscellaneous glitches of Pokémon Ruby and Sapphire, Pokémon FireRed and LeafGreen and Pokémon Emerald

Exclusive to Ruby and Sapphire:
256x item selling price glitch | Amazing Trainers | Berry glitch | Draining hitpoints animation glitch | Evolution animation glitch | Sticky Hold glitch | Mossdeep City Skitty glitch | Truck glitch | Nightmare glitch | Mossdeep City Skitty glitch
Acro Bike instability glitches (Japanese only) | Dark red selector glitch (International only) | Excessive doll arrangement glitch (Japanese only) | Mail and Trick glitches (Japanese only) | Surf on land (Japanese only)

Exclusive to FireRed and LeafGreen:
Celadon City origin glitch | Pokédex species glitch | Roaming Pokémon Roar glitch

Exclusive to Emerald:
Battle Pike poison knockout glitch | Black curtains glitch | Mart worker glitch | Mover Vigoroth cry glitch (Japanese only)

In various or all entries:
Azurill gender glitch | Boss HP recruit glitch (Mystery Dungeon) | Decamark-specific glitches | Dewford Gym footprint glitch | Evolution move-learning glitch | Focus Punch glitch | Roaming Pokémon IV glitch | Sky Pillar glitch | Thunderbolt glitch | VBlank RNG interrupt glitch

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This article is incomplete. Please feel free to add any missing information about the subject. It is missing: {{{1}}}.

The Pomeg glitch or Pomeg Berry glitch is an oversight regarding the Pomeg Berry's ability of lowering HP EVs, such that if the player uses a Pomeg Berry at a relatively low amount of HP, there is a possibility that relevant Pokémon's hitpoints will drop below zero and roll down from (2^16)-1 or 65535 HP due to hitpoints being a signed integer.

The consequences of the glitch vary between the game which it was exploited on, although the ability for the player to reduce a Pokémon's HP to essentially 'negative HP' via a Pomeg Berry has not been amended and if at all at least since the beginning of later fourth generation handheld Pokémon games.

Requirements

1. A Pomeg berry; ideally several of them.
2. A Pokémon with at least 10 HP EVs
3. A Pokémon with a relatively low amount of HP; this will depend on the level of the Pokémon, and can be a higher value if the Pokémon has more than 110 HP EVs.

Procedure

1. Obtain a Pokémon with a relatively low amount of HP and at least 10 HP effort values.
2. Use a Pomeg Berry such that the amount of HP that the Pokémon has drops below -1 (65535) or lower.

Additional purposes

Once a Pokémon receives an abnormal amount of HP, the glitch can be exploited to abuse many other oversights in the game engine, or "sub-glitches".

Pokémon Emerald

Battling with an Egg

In Pokémon Emerald, the Pomeg glitch is often exploited to allow unhatched Eggs to battle and is perhaps one of the most well known examples of Pomeg Berry "sub-glitches". To perform this trick, the player should only have an Egg in his or her party and another Pokémon with a relatively low amount of HP (which the Pomeg Berry will be used on). The player must then use the Pomeg Berry such that its HP depletes below -1 (65535) and use any healing item such as a Potion. Regardless of the value, the relevant Pokémon's HP will 'increase' back to zero.
The player cannot simply use the Pomeg Berry to deplete the Pokémon's HP to zero from a valid amount of HP as this will activate a black out; hence the Pokémon's HP must be depleted to at least -1 (65535) first.
By switching the Egg as the first 'Pokémon' in the party, and entering a battle, the Pokémon inside the egg will battle (with an egg-colored sprite), and can gain experience points in this way. The Pokémon inside of the Egg is capable of levelling up, hence it is possible to hatch an Egg into a Pokémon in a secondary or final evolutionary stage.

Notes

1. Shedinja cannot be used to exploit the Pomeg glitch because regardless of the amount of its effort value in hitpoints its HP will always remain at 1.