Sonic Mars was a concept game that was cancelled for unknown reasons (though it likely had something to do with the limitations and ultimate failure of the Sega 32X), before eventually being reworked into what eventually became Sonic X-treme.

In 2007, two different scripts were leaked for the cancelled game. The first, written by Michael Kosaka, focused on the 3D graphics and notably included elements from the 1993 Sonic the Hedgehog television series (referred to by fans as "Sonic SatAM"), which was airing at the time. The second, written by Don Goddard, focused more on how the game combined 3D graphics with 2D sprites, and dropped the SatAM elements.