From Bulbapedia, the community-driven Pokémon encyclopedia.
The Xtra Deck is a theme Half Deck from Pokémon Play It! It predominantly focuses on -type Pokémon.
In Pokémon Play It!, it is one of four decks available for the player. Julie always uses the Fighting Deck against it. She never uses the deck herself. Due to a programming oversight, no Energy card is discarded from Magmar when using the Flamethrower attack.
It is the only original version deck not featured on any level of Pokémon Play It! Version 2.