Nintendo hid a NES emulator inside GameCube's Animal Crossing

Fans of the early-2000s era GameCube version of the original Animal Crossing likely remember the game including a handful of emulated NES titles that could be played by obtaining in-game items for your house. What players back then didn't know is that the NES emulator in Animal Crossing can also be used to play any generic NES ROM stored on a GameCube memory card.

One has to wonder if there's any code from open source emulators in there.