Dual-slot mode (Japanese: ダブルスロット Double-Slot) is a method of communication between a Nintendo DS game card and a Game Boy Advance game cartridge by inserting both into the same Nintendo DS system. However, due to the removal of the GBA slot, dual-slot mode is not available if the player is using a system from the Nintendo DSi family or Nintendo 3DS family.
In the core series games
Pal Park
Main article: Pal ParkIn Pokémon Diamond, Pearl, Platinum, HeartGold, and SoulSilver, Pal Park allows the player to transfer Pokémon from Pokémon Ruby, Sapphire, Emerald, FireRed, and LeafGreen, using dual-slot mode for communication. The Pokémon are sent from the Generation III game to the Generation IV game and cannot be sent back.
Both games must be the same language in order to migrate Pokémon via Pal Park, unless the Generation IV game is Korean, in which case Japanese or English language Generation III games can be used.
Dongle method
In Pokémon Diamond, Pearl, and Platinum, the dongle method changes the wild Pokémon that appear based on the game in the Game Boy Advance slot, via dual-slot mode. This method is compatible with any of the Generation III core series games: Pokémon Ruby, Sapphire, Emerald, FireRed, and LeafGreen. The name "dongle method" is an unofficial name that comes from the fact that this method uses the Game Boy Advance game as a dongle for the Nintendo DS game.
After obtaining the National Pokédex, if the player had an applicable GBA game inserted in the GBA slot when they opened the title screen, the dongle method allows specific wild Pokémon to appear depending on the GBA game. Wild encounters will not change if a GBA game is inserted or removed from the Nintendo DS system after the title screen. The dongle method works regardless of the language of the GBA game (unlike with Pal Park).
The wild Pokémon that can appear this way are mostly not in the Sinnoh Pokédex in Pokémon Diamond and Pearl. They are usually version-exclusive Pokémon to one of the Generation III games. They usually have an 8% chance of appearing, or 4% each if there are two different Pokémon that can appear this way in the same location due to the same game.
List of Pokémon available using the dongle method
Accessories and Backdrops
In Pokémon Diamond, Pearl, Platinum, HeartGold, and SoulSilver, the player can obtain one unique Backdrop or Accessory for each Generation III core series game from a Lady in the Pal Park lobby, based on the game the player has inserted in the GBA slot. The lady describes the item as a gift for the player as a reward for their performance in a Catching Show (regardless of whether the player has ever actually participated in one).
Each gift may only be received once, and the player must leave and re-enter the Pal Park building to receive a new gift, even if the game is reset. The language of the GBA game is ignored, meaning that the player can receive a gift even if they would not be able to migrate Pokémon from it.
Event distributions
In the Generation IV core series games, some event distributions were done using a Slot 2 cartridge, which was inserted into the GBA slot to send data to the DS game card.
In spin-off games
Pokémon Dash
Japanese/Korean version cup display 
American/European version cup displayIn Pokémon Dash, players can make custom cups based on the party in a Generation III core series game inserted in the GBA slot. Pokémon FireRed and LeafGreen sprites are used (except for Speed Forme Deoxys, which uses its Pokémon Emerald sprite as it did not exist in FireRed and LeafGreen). Deoxys and Unown forms and Spinda patterns are retained, but Shiny coloration is not depicted. Eggs in the player's party are ignored.
The Japanese, European, and American versions of Pokémon Dash have no region checks, allowing the player use any language game (although only the first 5 characters of a Pokémon's name will be displayed in the Japanese version of Pokémon Dash). The Korean version only allows Japanese game cartridges to be used.
Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team
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In Pokémon Mystery Dungeon: Blue Rescue Team, dual-slot mode allows the game to communicate with Pokémon Mystery Dungeon: Red Rescue Team.
If the player has both games inserted into a compatible system, SOS Mail can be sent between the games, allowing for the rescue team in one game to save the team in the other cartridge's save file.
In Pokémon Mystery Dungeon: Blue Rescue Team, the player can use Receive Team while Red Rescue Team is in the Game Boy Advance slot. If used, the rescue team from Red Rescue Team becomes the boss of the Rescue Team Maze of Makuhita Dojo. The rescue team can be recruited into Blue Rescue Team using species recruitment rates (although some Pokémon such as the legendary birds cannot be recruited this way, potentially to avoid having duplicate Legendaries in Friend Areas with more than one slot).
Trivia
In other languages
See also
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