From Bulbapedia, the community-driven Pokémon encyclopedia.
Up to four people can play together with only one available CPU player. Players have the option of setting the CPU's difficulty from Easy, Normal, and Hard. Players can form teams each choosing 3 Pokémon and players can decide who goes first by selecting their Pokémon first on the selection screen. Pressing L will reset all players Pokémon choices on the selection screen allowing the players to choose again. Holding the R button will allow the player to check which Pokémon they have selected alongside their partners on the selection screen. Players use the A, B, and C buttons to select the Pokémon they will use, and once all six have been chosen the battle will begin.
As [[Double Battle]]s did not exist in the first and second generations, if more than two people play, up to two will be on a "team". Each player on such a team will choose six of either their own Pokémon from a
R/B/Y game inserted into a [[Transfer Pak]] that is connected to their controller, or they may choose from a selection of the rental Pokémon available to them. During the team preview, each of these two players may choose three of the Pokémon they wish to enter in that particular battle. Players will only have control over the Pokémon they selected. In order to switch to a teammate's Pokémon, that teammate must press B to switch to another Pokémon, and then press the corresponding C button, depending on which Pokémon they want. A player can only switch to their own Pokémon.
In both games, players may also choose which stadium to battle in. Each stadium has a different appearance, and and some are based off of environments from [[Kanto]] and [[Johto]]. Players battle until the opposing trainers Pokémon are knocked out.