To activeate the following cheats which can be used during battle, hold down the target button the enter R,R,L,L,R,L,R using the directional pad. You should then hear a sound, from there you can enter the following codes: Baby Players - WP, SP, SK, WK, Target.
Big Heads - Z.
Big Feet - R.
Green Nose - WP, WP, R.
Invisibilty - SK, SK, SK, WK, crouch.
Invisibility (Fighter and Opponent) - SK, SK, SK, WK, A.
One-hit Kills - SP, SP, SP, WK, WK, WK, R.
Polygon Fighters - SP, SP, A.
Purple Nose - WP, WP, Z.
Red Nose - WP, WP, A.
Slippery Stages - WP, WP, WP, WK, WK, WK, A.
Take No Damage - SP, SP, SP, WK, WK, WK, A.
Take Less Damage - SP, SP, SP, WK, WK, WK, Z.