When in Juggler, or Dragonfly press Select+A+B+R+L at the same time, and you will get access to a secret menu. In Juggler, you can adjust how many points you get for different things in the level, or adjust infinite lives, etc.
NOTES: When adjusting points, hold L until the points go past zero, then hold R to get 99,999 points for each thing!
Do not adjust "Jump velocity" past 3,500. Otherwise you will start bouncing around the screen and your character will be uncontrollable.
In Dragonfly, you can adjust the frequency that different monsters appear.
This menu is not available in Magna Racer.