Finally—the ability to play as Tingle.
There's never been anything quite like the GameCube/Game Boy Advance Link Cable. You might say its first iteration was the N64's Transfer Pak, used exclusively with the Pokémon Stadium games. With that handy device, which plugged into the port at the bottom of the N64 controller, players could actually plug their Pokémon games into the N64 and upload their incredible teams for 3D fighting championships. It was pretty awesome, and when the GameCube came around, Nintendo decided to take things a step further. The Wii and DS haven't seen this kind of connectivity proliferation, but next year, Nintendo is basically taking the GBA/GC link cable and making it THE system, so let's see where things began.
The GC/GBA Link Cable attached a player's GBA to a GameCube controller port. While generally used to unlock features in either the GC or GBA versions of a certain game (or both), there were also instances where the player controlled the action on the GC with their GBA as a controller. The cable was compatible with the GBA "classic," GBA SP, and even the e-Reader. Thanks to backwards compatibility, the cable is able to plug into the Wii's GC controller ports. While many games were able to utilize GC/GBA connectivity (it's a big list), there are a few famous examples I'd like to go over here, and then Pedro Hernandez has some things to say about his experience with the technology.
The Legend of Zelda: Four Swords Adventures took full and imaginative use of the link cable in a way that predicted the Wii U. Up to four players, all with GBAs and link cables (not cheap) plugged their handhelds into the GC and actually used the GBAs as controllers to move their Link on the TV. Whenever somebody entered a house or cave, they disappeared from the TV screen but appeared individually on their individual GBA screen. A direct descendant of the Four Swords multiplayer game included in the GBA port of A Link to the Past, Four Swords Adventures challenged players to cooperate to solve puzzles and defeat enemies while also competing for special items and rupees ("Force Gems").
In The Legend of Zelda: Wind Waker, after Link rescues Tingle from the Windfall Island prison, a second player can plug his or her GBA into the 2nd player controller port and control a disembodied Tingle as he helps Link defeat enemies and get items. The GBA displays an overhead map of wherever Link is as well as the hero's position. The player controlling Tingle can use rupees from Link's inventory to do a variety of helpful actions, including allowing Link to walk on air for five seconds, drop bombs on enemies or breakable objects, buy certain items on the spot, and fill up hearts and/or magic. If you're trying to get 100% of the items in the game, you will need to use the Tingle Tuner.
Mario Golf: Toadstool Tour (GC) and Mario Golf: Advance Tour (GBA) featured an interesting transfer system. The GBA game allowed players to customize and build up their characters in an RPG-like fashion. The Link Cable allowed you to transfer your custom character to the bright 3D fairways of the GC game. Experience earned playing the GC game was transferred back to the GBA game.
Metroid Prime (GC) and Metroid Fusion (GBA) had their own special brand of connectivity. Once a player beat both games, linking the two up caused Samus' craptastic Fusion Suit to become available in Metroid Prime, as well as the original NES Metroid. Unless my memory fails me (which it does--I'm old), some Fusion concept art also showed up in Prime's concept art roster. Unfortunately, the GBA game itself didn’t get any unlocks. Linking Metroid Fusion and Metroid Zero Mission, however, does unlock extra illustrations in the former game which chronicle Samus' early days with the Chozo and making me thirst for a game that takes place during that era.
Pac Man Vs. is an interesting game in that its only option is multiplayer: while three players control Ghosts with GameCube controllers (watching the TV screen), one player is Pac-Man on the GBA. Pac-Man can see the entire maze, but the Ghosts can only see a limited view around themselves. An on-screen radar tells the ghosts when they are close to each other. As always, Pac-Man's goal is to eat all the pellets in a stage without being touched by Ghosts. If a Ghost catches up with Pac-Man, the players trade controllers, so there's a good deal of back-and-forth. Unfortunately, the game is multiplayer ONLY. If there are fewer than three players as Ghosts, NPC Ghosts are grey and cannot hurt Pac-Man. However, the Ghost player(s) can touch the grey Ghost and turn it into their own AI-controlled pawn (who is then deadly to Pac-Man).
And now, here's Pedro’s take on Animal Crossing's connectivity features, which seem to rival those of anything before (or after) it.
Animal Crossing was, at its heart, one of Nintendo's most experimental games on the GameCube. It being a new franchise allowed Nintendo to show off new gameplay concepts without compromising the legacy of an already existing series. One of the most memorable and heavily advertised was the connectivity between the GameCube and Game Boy Advance. Even if games like Four Swords Adventure prominently used it to better effect in terms of being a vital tool in gameplay, Animal Crossing had the most uniquely fun features of any game to use the connectivity.
The first feature that would be unlocked once you connected the two systems was Animal Island, a new area where players could visit an island villager and gain a second house to either store their stuff or use as a tropical home. When the game detected that the Game Boy Advance was connected, Kapp'n (Animal Crossing's resident chauffeur) would appear on the dock, asking the player if they wished to visit Animal Island. As neat as this sounds, there was another thing you could do with Animal Island. You had the option of downloading Animal Island onto the Game Boy Advance, where you could feed your own islander character and gain new features in the regular game.
The second most memorable connectivity feature was the e-Reader. The e-Reader was a peripheral for the Game Boy Advance with which players could scan cards and unlock features throughout several Nintendo games. In Animal Crossing, players could buy Animal Crossing cards that, when used by themselves, could unlock extra features using the game's code system. But if you connected your Game Boy Advance to the GameCube while the e-Reader was in place, scanning the cards would unlock even more items in the game, from rare furniture pieces to NES games.
The e-Reader would sadly be shortly lived, as Nintendo stopped supporting it nearly a year later, and many players felt it was tedious to slowly scan cards just to unlock content (though several Pokemon cards still had data written onto them). But it was a quirky experiment that felt very much like a Nintendo product in its execution, and in Animal Crossing it further extended the already long replay value of the title.
Creativity was also one of Animal Crossing's strongest assets. Players could design textures to wear as part of their clothing. If they felt limited by the GameCube interface, they could instead download the feature onto the Game Boy Advance, design their textures, then upload them onto the GameCube game.
Finally, players would be able to transfer NES games and store them on the Game Boy Advance. The game would be stored on the system's memory and as long as the player didn't turn the system off, they could play it for hours on end.
Those are the connectivity features in a nutshell. None of these were necessary to enjoy the core concept of Animal Crossing's gameplay, but players who decided to invest in these peripherals would see the game's value and creativity rise through the roof. To this day, it remains one of the best and most fun uses of the fabled GameCube to GBA link, and one worthy of being celebrated on the GameCube's 10th anniversary.
Couldn't have said it better myself, Pedro, mostly because I didn't play Animal Crossing. I did get all the Tingle Statues though, so good for me. Well, folks, in preparation for the GC's impending double-digit birthday, I suggest you all get out your rusty old Link Cables, track down some people with Game Boy Advances, and run Ganon out of town in Four Swords Adventures. HUZZAH!