All Weapons And Missions
Press L, Black, White, R(2), White, Black, L at the main menu.

Unlimited Ammunition
Press Start to pause game play, then press R, L, Black(2), White, R, L, Black, 
White. Repeat this code to disable its effect.

Invincibility
Press Start to pause game play, then press L(3), Black, L, R(2), L, Black. Repeat 
this code to disable its effect.

Stay In Snowmobile
Play The Training Wheels level. When you are near the extreme temperature 
rooms, transform into the escape cycle. When you go over the snow, it will 
automatically turn into a snowmobile. However, it will stay a snowmobile even 
when you get out of the snow until you finish stage 3.