GameShark

GameShark is a cheating device used to alter the internal data of many video games. It is well-known for its use in the Pokémon series, as it is one of the ways to easily get legendary Pokémon or Pokémon only available through an event, and many rare items, such as Master Balls.

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Game shark has an unwanted tendency to erase saved games. If you do not put the game into the gs correctly, the start screen won't show up. If you keep turning it on and off, even w/o removing it then your data is erased.