First clear the game's Final Stage and save it to a memory card. Cynthia will now be available.
Make Own Puzzles
First clear the game's Final Stage and save it to a memory card. Now go into Options and select Game Mode. Choose System and press Right to turn Original Mode On. Exit Options and select the 1p game.
Play as Spike
Beat the game with Cynthia and have an IQ over 400.
Play Demo Levels
At the Rules highlight either Demo 1 2 or 3 then hold L1 R1 and press X.