EX Hidden Legends is an Expansion of cards and Theme Decks for the Pokémon TCG that completed transferring all of the Generation III Pokémon into card forms. Nintendo temped TCG enthusiasts by issuing Swalot as a prerelease card in the U.S. on the weekends of 5th/6th and 12th/13th June 2004. The set introduced several dual-type Pokemon, including Psychic and Metal. Nintendo also change the holographic design with this set by implementing reverse holograms. Instead of the previous holographic design, the same foil was used with an energy symbol pattern. The Pokemon type was also shown as a small foil symbol in the attack box. The reverse-holographic design has changed with each subsequent Expansion.