Prerelease cards are reprints of one selected card from a Pokémon Trading Card Game expansion with a foil "PRERELEASE" stamp or the expansion's logo in the bottom right corner of the card illustration.
Wizards of the Coast first produced Prerelease cards when the TCG was first localised, and were given to participants of the early test leagues of what would later become the Pokémon League. Prerelease cards were then only awarded through select sites of the Pokémon League for the next three expansions before Wizards ceased their production. After Pokémon USA acquired the TCG license and fully established the Play! Pokémon program, Prerelease events were set up to coincide with the release of the upcoming expansions. In the United States, Prerelease events are typically held over two weekends prior to the commercial release of expansions, and have continued to be an integral part of the TCG calendar.
Officially, there were only four Prerelease cards released by Wizards. However, whilst printing a test run of Jungle Clefable cards (a trial of the Prerelease cards for the Pokémon League), several Base Set Raichu cards were erroneously added to the sheet, and therefore also included a Prerelease stamp. The error was corrected and the Raichu cards were apparently given to Wizards employees. Despite this common knowledge within the TCG community, Wizards continued to deny their existence for years.
Luxio from Diamond & Pearl was the first Prerelease card to have a "STAFF" stamped version, for the Prerelease event organizers. Cards released thereafter have continued to feature STAFF versions as well as a normal version.
Buck's Training from Legends Awakened was the first non-Pokémon Prerelease card.
With the release of HeartGold & SoulSilver, Prerelease cards no longer feature the "PRERELEASE" stamp, and instead feature the expansion logo. Also, ever since the release of HeartGold & SoulSilver, all of the cards have been Rare cards in the expansion.
Starting from the Dark Explorers expansion until the end of the Black & White Series, all Prerelease cards were actual promotional cards and featured alternate art. Only for the XY expansion, the Prerelease promos returned to specially stamped cards in the expansion. They returned to be XY Black Star Promos for the second XY expansion, Flashfire.
Starting from the Fates Collide expansion, there are four available Prerelease cards, released in Prerelease Kits.