Mario Kart (NES)
An NES bootleg that was sought after for years, Nice Code's Mario Kart is an advanced hack of Nintendo's F-1 Race that only ever appeared on rare Spanish plug & plays.
Unused Game Over
On the title screen, press Right before pressing Start (a sound effect will accompany this) to get an instant game over when the race starts. There is no way to get a game over normally, making this an unused function.
A little Super Mario Bros.-styled Mario in his kart.
The aforementioned unused "Game Over".
An unused "Pass".
An unused "Time Out".