From Bulbapedia, the community-driven Pokémon encyclopedia.
A Battle Pass is an item used in Pokémon Battle Revolution that must be used to compete in Pokétopian Colosseums. Pokémon on the selected pass act as the player's party Pokémon for the duration of the current challenge. There are three kinds of passes, Rental Passes, Custom Passes, and Friend Passes. Each of these kinds of passes can be used in a free battle as the player (except for Friend Passes) or as the opponent.
List of Passes
These Passes are pre-set by the game, and come with predetermined rental Pokémon (usually ones in their middle evolutionary stage). However, once players unlock Trade Battles at the Gateway Colosseum, the Pokémon may be traded with opponents. The player starts with only one, chosen at the start, but can earn more by borrowing them for a Rental Battle at the Gateway Colosseum. The choice of Rental Passes expands as the game progresses. These may be used if the player cannot upload Pokémon from their Generation IV games or in the case they do not own a Generation IV game, and must be used in Gateway Colosseum.
These Passes can be made by player using Pokémon from their Generation IV games. Each has a different background, which is selected when the Pass is created. Any Pokémon can be used on these, though Pokémon used on another Pass cannot be used. If the player's Pokémon are of varied levels, the opponent will use Pokémon at the level of the highest level Pokémon on the player's pass. If a player uploads a Pokémon onto one of these passes and then deletes it in the game, the Pokémon will appear shadowed. It can still be used, but if removed, it's gone for good. This also occurs if one uses certain Action Replay codes to make a Pokémon with stats that are too high. These passes can be used at almost every Colosseum in Pokétopia except Gateway Colosseum.
These Passes are obtained after battling other players over the Nintendo Wi-Fi Connection and trading Friend Passes. They contain the standard information about opponents, like name, location, and number of battles. They can also be stored on a Wii Remote and sent to other players by sharing data. However, Friend Passes can only be used during Free Battle mode; use during Colosseum Battle mode or Wi-Fi Connection is prohibited.