HM05 (or Hidden Machine 05) is able to permanently teach a Pokémon a move for use outside of battles. It made its debut in the first generation allowing a Pokémon to learn Flash. In the second and third generation games it allows for a Pokémon to learn Flash (as well as in Mystery Dungeon). In the fourth it allows for a Pokémon to learn Defog (in Diamond, Pearl and Platinum) and Whirlpool (in HeartGold and SoulSilver). In the fifth generation games it allows for a Pokémon to learn Waterfall.