Roaming Pokémon IV 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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Bulbapedia also has an article about Roaming Pokémon IV glitch.

The Roaming Pokémon IV glitch occurs in Pokémon Ruby and Sapphire, Pokémon FireRed and LeafGreen and was patched in Pokémon Emerald.

It causes roaming Pokémon (Latias, Latios, Raikou, Entei and Suicune) to always have 0 IVs in the Special Attack, Special Defense, Defence and Speed stats, and a maximum 7 IVs in the Attack stat. The HP IV is unaffected by the glitch.

See also

1. Roaming Pokémon Roar glitch