There are several early Pokémon TCG products that served as an introduction to the Pokémon Trading Card Game for the US market. It is believed that these items were released as early as 1998, before even Base Set was released.
The first of these items was the Pokémon TCG "Demo Game" booster pack. This booster pack was designed for two players and contained 24 shadowless Base Set cards and an instruction booklet. It is believed that these booster were distributed to retailers so that customers could sample the game. They were not intended for public sale.