Dual-type damage misinformation

Dual-type damage misinformation is a glitch that causes incorrect type effectiveness messages to be displayed against dual-type Pokémon in Generation I games.

Mechanics

In Generation I, Pokémon with two types that have a weakness and resistance to the same type receive neutral damage from that type, but the incorrect message is displayed.

For example, Grass-type moves do neutral damage to Gyarados, but if Gyarados is hit by a Grass-type move, the game erroneously states that the attack is "not very effective...".

The game prioritizes on which message to display for each 'special' scenario (where normal damage is not dealt) based on each scenario's internal ordering. The higher the ordering determines what message the game will display. Grass against Water as 200% damage for instance is the 4th entry, whilst Grass against Flying as 50% damage is the 27th. Consequently, in this example, the game chooses the message for scenario #27, returning the wrong message "It's not very effective...".

This glitch does not occur in Pokémon Stadium.

By Wooggle

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If an attack is super effective or not very effective against one type and does no damage against another type (for example, Dig against Charizard), the game will erroneously state that the attack missed.

Order of priority of messages

This list is presented in the reverse order to which they are stored in the game data. Messages higher on the list take priority over those lower on the list.

Attacking type Effectiveness Defending type Dragon 2× Dragon Ice 2× Dragon Grass ½× Dragon Electric ½× Dragon Water ½× Dragon Fire ½× Dragon Ghost 0× Psychic Ghost 0× Normal Rock 2× Ice Rock 2× Bug Rock 2× Flying Rock ½× Ground Rock ½× Fighting Rock 2× Fire Bug 2× Poison Bug ½× Ghost Bug 2× Psychic Bug ½× Flying Bug ½× Fighting Bug 2× Grass Bug ½× Fire Psychic 2× Poison Psychic 2× Fighting Flying ½× Rock Flying 2× Grass Flying 2× Bug Flying 2× Fighting Flying ½× Electric Ground 2× Poison Ground 2× Rock Ground ½× Bug Ground ½× Grass Ground 2× Electric Ground 2× Fire Poison ½× Ghost Poison ½× Rock Poison 2× Bug Poison ½× Ground Poison ½× Poison Poison 2× Grass Fighting 0× Ghost Fighting 2× Ice Fighting 2× Rock Fighting ½× Bug Fighting ½× Psychic Fighting ½× Flying Fighting ½× Poison Fighting 2× Normal Ice 2× Flying Ice 2× Ground Ice 2× Grass Ice ½× Water Grass ½× Flying Grass 2× Rock Grass ½× Poison Grass ½× Bug Grass 2× Ground Electric 2× Flying Electric 0× Ground Water 2× Ground Fire ½× Rock Fire 2× Bug Ghost 2× Ghost Normal 0× Ghost Normal ½× Rock Electric ½× Grass Water ½× Grass Grass ½× Fire Fire ½× Water Psychic ½× Psychic Grass ½× Grass Ice ½× Ice Electric ½× Electric Fire ½× Fire Water ½× Water Ground 0× Flying Water 2× Rock Electric 2× Water Grass 2× Water Fire 2× Ice Fire 2× Grass Water 2× Fire

The text for Dragon being super effective against Dragon is unused as the only Dragon type move in Generation I was Dragon Rage, a move that does a fixed 40 damage to the target that is unaffected by type effectiveness.

Related articles

Glitches in the Pokémon games Transform glitches • Glitch Trainers • Cloning glitches • Error messages • Arbitrary code execution Generation I Glitches • Battle glitches • Overworld glitches -- • 0 ERROR • Broken hidden items • Cable Club escape glitch • Dual-type damage misinformation Experience underflow glitch • Fight Safari Zone Pokémon trick • Glitch City • Item duplication glitch • Item underflow Mew glitch • Old man glitch • Pewter Gym skip glitch • Pokémon merge glitch • Rhydon glitch • Rival twins glitch Select glitches (dokokashira door glitch, second type glitch) • Super Glitch Time Capsule exploit • Walking through walls • ZZAZZ glitch Generation II Glitches • Battle glitches Bug-Catching Contest glitch • Celebi Egg glitch • Coin Case glitches • Experience underflow glitch Glitch dimension • Glitch Egg • Teru-sama • Time Capsule exploit • Trainer House glitches • GS Ball mail glitch Generation III Glitches • Battle glitches • Overworld glitches Berry glitch • Dive glitch • Pomeg glitch • Glitzer Popping Generation IV Glitches • Battle glitches • Overworld glitches Acid rain • GTS glitches • Pomeg glitch • Rage glitch Surf glitch • Tweaking • Pal Park Retire glitch Generation V Glitches • Battle glitches • Overworld glitches Charge Beam additional effect chance glitch • Charge move replacement glitch • Choice item lock glitch Frozen Zoroark glitch • Sky Drop glitch Generation VI Glitches • Battle glitches • Overworld glitches Charge Beam additional effect chance glitch • Charge move replacement glitch • Choice item lock glitch Lumiose City save glitch • Symbiosis Eject Button glitch • Toxic sure-hit glitch Generation VII Glitches • Battle glitches • Overworld glitches Charge Beam additional effect chance glitch • Charge move replacement glitch • Choice item lock glitch Toxic sure-hit glitch • Rollout storage glitch Generation VIII Glitches Charge Beam additional effect chance glitch • Charge move replacement glitch • Choice item lock glitch Toxic sure-hit glitch • Rollout storage glitch • Party item offset glitch Generation IX Glitches Glitch effects Game freeze • Glitch battle • Glitch song Gen I only: Glitch screen • TMTRAINER effect • Inverted sprite Gen II only: Glitch dimension Lists Glitches (GO • HOME • Mystery Dungeon • TCG GB • Spin-off) Glitch Pokémon (Gen I • Gen II • Gen III • Gen IV • Gen V • Gen VI • Gen VII • Gen VIII) Glitch moves (Gen I) • Glitch types (Gen I • Gen II)

This glitch Pokémon article is part of Project GlitchDex, a Bulbapedia project that aims to write comprehensive articles on glitches in the Pokémon games.