In Animal Crossing, you could play classic games on NES consoles. But there was a console that was not bundled with a game and had no use. Apparently, that unit can be used as an in-game NES emulator.
If you owned a Nintendo GameCube, there was also the chance that you owned Animal Crossing. The community simulation game was quite popular at the time, offering many different kinds of activities, with one of those being able to play video games in your own home.
While some of the consoles had games attached, there was one that was completely on its own. Trying to get this console to work was often met with failure and many just assumed that the console was simply made for decoration. But according to security researcher James Chambers, when you activate the console, what it is actually is doing is scanning memory cards attached to the GameCube, seeking ROM files opening the possibility to play supplied NES ROMs.
Chambers was originally looking about for hidden developer menus and noticed that these areas were also connected to the NES console found in the game. Despite locating and trying to execute files, there were certain issues, and the console would crash when loading a ROM file from the memory card. With a lot of trial and error, and exploring, which Chambers goes into heavy detail on his blog, he found a way to have the built-in emulator play games that weren’t natively built into Animal Crossing. Mind you, the ROMs must be formatted a certain way for the game to understand them but it can play your favorites.
It’s interesting to think that something like this was actually in the game the whole time and someone was able to discover it nearly two decades after the game was first released. Again, if you want the full details on how Chambers accomplished his feat, be sure to check out his website.
Source: James Chambers via Ars Technica