Transfer Pak
The Transfer Pak was an accessory for the Nintendo 64 that allowed for connectivity between Nintendo 64 games and Game Boy or Game Boy Color games. Much like other Nintendo 64 accessories, it plugged into the back of the Nintendo 64 Controller. A Transfer Pak came packaged with each copy of the first Pokémon Stadium in America and Europe although the first game to use it was the original Pokémon Stadium in Japan. The Stadium series's biggest draw was that one could use the Transfer Pak to take their Pokémon from the Red, Blue, and Yellow Versions or Gold, Silver, and Crystal Versions to use them in battle as opposed to the game's rental Pokémon that had preset moves and stats. It also allowed for the inserted game to be played on the TV Screen through the use of the Stadium's GB Tower.
Some interesting notes, if a Pokémon Yellow's Pikachu was used to win a certain tournament in the first Pokémon Stadium, an event would be unlocked in the Game Boy game to allow that Pikachu to learn Surf. For the second game, there was an option to view the player's customizable room from Gold, Silver, and Crystal. After a certain point in the second generation games was reached, an event would open up to let player take part in a Mystery Gift with an in-game character. A handy feature for those without the means do it with other players.
The Transfer Pak was also a compatible with the Mario Golf and Mario Tennis games. Personalized characters from the Game Boy Color versions could be transferred over to be played with on the N64 versions. Those characters could also earn experience while playing through the various modes in the console games that would be carried over when they were transferred back into the handheld games.
Mario Tennis also utilized the Transfer Pak better than Mario Golf. While transferred characters from Mario Golf had to be transferred back into the N64 game every time the game was turned on, Mario Tennis transfers stayed in the N64 game even after shutting it off. Mario Tennis could also unlock various Mario characters for the GBC game. Completing these character's mini-games on the handheld game would unlock courts to be used for the N64 game.
Other games in America to take advantage of the Transfer Pak were Perfect Dark and Mickey's Speedway USA with their respective GBC versions. It was necessary in Mickey's Speedway to unlock one of the characters and for Perfect Dark it unlocked various weapons and secrets. In the first stages of Perfect Dark, there were plans to use the Game Boy Camera to import photos and map the faces over in-game character models, but the function was later scrapped. In Japan, the Game Boy Camera would be used for simply transferring photos over to be decorated in one of the Mario Artist games for the Nintendo 64DD.
While the Transfer Pak didn't see much support overseas, it received much better support in Japan with at least ten other games from third parties taking advantage of the function.
The Transfer Pak's ability to connect console and handheld games was succeeded by the Nintendo GameCube Game Boy Advance Cable
Transfer Pak functionality has yet to be properly emulated by the Wii's Virtual Console.