Multiplayer in Animal Crossing on GameCube
The 2002 game had no online play and no two players on screen at once. This site adds live visits between towns over the internet. Both halves are below, kept apart so it is always clear which is which.
The original: four people, one town, one at a time
A GameCube town holds four residents. They share the land, the shop, the villagers, the clock, the museum and the town tune, and each keeps their own house, pockets, wallet, catalogue and designs. What they never do is play at the same time.
There is no split screen and no same-screen co-op. That is not a design opinion, it is three separate facts about how the game is built: it creates exactly one player character and every part of the code reaches for that same one, it reads only controller port one for gameplay, and it has a single camera with no way to divide the screen. Switching residents means saving, quitting to the player-select screen, and coming back as someone else.
So the four of you take turns, and you meet through what you leave behind: letters, the note on your gyroid, items in each other's houses, and things put up for sale.
Visiting a friend, live
Everything below is ours. None of it is in the GameCube game, and none of it will be in a copy you play anywhere else.
Sign in, open the Friends panel on the play screen, and send a visit request by user id or invite link. When it is accepted, walk to your train station and ride in. You arrive through Porter the same way the original did it, and then you are both standing in the same town at the same time.
You see each other walk and run, use tools with full animation, and pop up emotes. The visitor is in the host's town, so they get the host's villagers, fish, bugs, weather, time of day, shop stock and town tune. Digging, chopping, shaking trees, the money rock, dropping and picking things up, planting, pulling weeds, signs, the bulletin board and item trades all show on both screens. Doors work, and you stay visible to each other indoors.