Mario Kart Fixed Circuit is a hypothetical, fan-made title based on the popular Mario Kart franchise. It doesn't represent an officially released game by Nintendo.  Gameplay would likely consist of kart racing with variations on the classic Mario Kart formula.  The "Fixed Circuit" component in the name might suggest a set of predetermined tracks or a focus on time trials, rather than the randomization typically seen in official Mario Kart games.

Mario Kart Fixed Circuit

Marheaven - Knockin' on Heaven's Door (J)(Supplex)