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.

Overview

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.

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.

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.

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