Narrow Gym

This card stays in play when you play it. Discard this card if another Stadium card comes into play.
No player may have more than 4 Pokémon on his or her Bench. When this card is played, if a player has 5 Pokémon on his or her Bench, that player chooses 1 of them and returns it and all cards attached to it to his or her hand. (If both players have to return a Pokemon, your opponent returns a Pokemon first.)