Every time basic mode is completed with a different character a new option will be unlocked, until the extra option menu is full.

Successfully complete basic mode with seven different characters. He looks like an old Fokker, but has different moves.

Successfully complete basic mode with eight different characters. She is the girl from shop mode and fights similarly to Julia.

Successfully complete basic mode with all characters, including Mel and Pride to unlock three new arenas exclusive to original mode. To access them, move the pointer left or right at the arena selection screen until it is off-screen. A large box with the "Extra Arena" message will appear. Select the desired extra arena. The arenas are a small room, a very narrow bridge over along drop, and a geometric (cubes stacked in weird patterns) arena.

If during the course of the game you manage to pick up item #103, which resembles a red turban, sell it for 100,000 credits in shop mode. This item seems to appear randomly.

Pause the game and press X + Y.