Key Items are unique, plot-critical items that cannot be sold or discarded. Hidden Machines (HMs) are special TMs that teach moves essential for navigating the world outside of battle.
Key Items:
- Pokédex: Records Pokémon data. (Given by Professor Oak)
- Town Map: Shows the Kanto region map. (Given by Blue's sister)
- Bicycle: Allows faster travel on land. (Obtained in Celadon City after getting a Bike Voucher)
- Itemfinder: Detects hidden items nearby. (Obtained on Route 11)
- Poké Flute: Wakes up sleeping Pokémon (Snorlax). (Obtained from Mr. Fuji in Lavender Town)
- Coin Case: Stores coins for the Game Corner. (Obtained in Celadon City)
- S.S. Ticket: Allows access to the S.S. Anne. (Obtained in Vermilion City)
- Lift Key: Unlocks the elevator in Team Rocket Hideout. (Obtained in Team Rocket Hideout)
- Silph Scope: Reveals Ghost-type Pokémon in Pokémon Tower. (Obtained in Team Rocket Hideout)
- Card Key: Unlocks doors in Silph Co. (Obtained in Silph Co.)
- Secret Key: Unlocks Cinnabar Island Gym. (Obtained in Cinnabar Mansion)
Hidden Machines (HMs):
- HM01 Cut: Cuts down small trees. (S.S. Anne Captain)
- HM02 Fly: Instantly travels to previously visited towns. (Route 16)
- HM03 Surf: Travels across water. (Safari Zone Warden)
- HM04 Strength: Moves large boulders. (Safari Zone Warden)
- HM05 Flash: Illuminates dark caves. (Route 2, after getting 10 Pokémon)
HMs are crucial for progression and exploration. Teach them to 'HM slaves' – Pokémon you don't use in battle but carry for their HM utility.
While Pokémon Yellow limits HM moves to five essential slots, later titles like Pokemon Emerald expanded this roster to eight, requiring more strategic party management for world navigation.
While Pokémon Yellow utilizes Key Items like the Pokédex to track progress, Pokemon TCG Live employs a similar collection-based system through its digital card gallery and deck-building interface.