From Bulbapedia, the community-driven Pokémon encyclopedia.
A Ball Capsule (Japanese: ボールカプセル Ball Capsule) is a special item introduced in Generation IV that can be attached to a Pokémon's Poké Ball to add special effects when the Pokémon is sent out in a battle.
In the games
Ball Capsules may be accessed from the player's own PC. There are twelve spaces for them to be saved on, and their appearance can be altered by adding Seals to their exteriors, which are used to create a variety of special effects. Most Seals can be purchased in the Sunyshore Market at Sunyshore City. A total of eight Seals can be attached to a Ball Capsule at one time.
If a Pokémon whose Poké Ball has a Ball Capsule is to be released or stored in the Pokémon Storage System, the Ball Capsule must be removed. Likewise, when a Pokémon is traded, the Ball Capsule will automatically be removed.
NPC Trainers in Pokémon Platinum use Ball Capsules, notable examples include the Sunyshore Gym Leader Volkner and the Elite Four member Flint, who use Ball Capsules on the Poké Balls of their Electivire and Magmortar, respectively.
Ball Capsules and Seals were removed in Generation V.
In the anime
Dawn demonstrating how to use a Ball Capsule in the anime
In the Pokémon anime, Ball Capsules are mainly used by Coordinators in Pokémon Contests held in the Sinnoh region to enhance a Pokémon's stage appearance, as it is important to make a good first impression right out of the Poké Ball.
In this canon, Ball Capsules were introduced in Mounting a Coordinator Assault!, in which Ash and Dawn were seen receiving a Ball Capsule each after registering for a Contest Pass. Ash had never heard of Ball Capsules before and so Dawn explained to him how they can be used in combination with Seals to add special effects when a Pokémon is sent out.
In Sinnoh, Coordinators will receive a Ball Capsule along with a variety of Seals, a Ribbon case, and a rule book when signing up for their first Pokémon Contest, but it is assumed that additional Capsules can be bought at Poké Marts, since Dawn has been seen with more than one Ball Capsule during competitions following the Double Performance format.
While Pokémon Contests seem to be their main use in the anime, they cannot be used during Super Contests in the games.
In the manga
In the Pokémon Adventures manga
In Knowledge of the Unown I, Platinum receives a Ball Capsule and some Seals as thanks for giving the Pokémon News Press information on Unown.
In other languages