In 2003, Nintendo and Sega released a futuristic racing game titled F-Zero GX for the Gamecube, co-developed by the two companies in collaboration and CO-produced by Shigeru Miyamoto and Yakuza director Toshihiro Nagoshi.
This game had an arcade counterpart called F-Zero AX, which shared tracks and features with the Gamecube version, and also had a few tracks that could be accessed on the Gamecube, but only with significant difficulty.
Last November, a group of F-Zero enthusiasts discovered that the Gamecube optical disc for F-Zero GX not only has the entire F-Zero AX game on it as well, but that it’s fully playable. The game can be accessed using Action Replay codes, which allow you to boot it up and play the arcade version.
While the discovery was made in November, it was only widely-publicized earlier this week by a site named RetroCollect. You can watch a video of the hidden F-Zero AX content in the video above.