#728 - AX on GX

The entire arcade version of F-Zero GX, called F-Zero AX, is actually hidden within the files of F-Zero GX and can be accessed and played via hacking. This took about a decade since the game's release to find.

SOURCE: http://www.nintendolife.com/news/2013/03/f_zero_ax_found_hidden_in_gamecube_f_zero_gx