The Lock Capsule (Japanese: ロックカプセル Lock Capsule) is a special key item present in Pokémon HeartGold and SoulSilver. It has no use in these games and has not yet been made legitimately available. Regardless, it does have a use in Pokémon Black and White. The Lock Capsule has two menu sprites, one for HeartGold and SoulSilver (top) and one for Black and White (bottom).
In-game data reveals the following about the Lock Capsule: a menu option "VIEW LOCK CAPSULE CARD", event data "The Lock Capsule is held in the strictest safekeeping." and "The Lock Capsule was delivered safely!", and item text "A sturdy Capsule that can only be opened with a special key." It cannot be obtained in game; it is expected to be made obtainable via a future event.
Its in-game data is similar to the Manaphy Egg that can be transferred from Pokémon Ranger to any of the five Generation IV main series games. The Lock Capsule itself is transferable to Pokémon Black and White. In these games, it can be opened to reveal the exclusive TM95 (Snarl).