Level Warp Codes:
Press pause and then press:

A+Left, X,X,X+B,X,A,XA+Left - Princess
L+A,A,R+A,A,B,B,X,B - Andy Asteroids
A,X,Left,Left,X+Y,Up,Down,Left - Buttville
Up, Down, Left+Down, Left, Down, Down, Up+Left, Down Down - The Tubes
A,B,X,A,B,X,A,B+R - For Pete's Sake
A+B, B+X, X+Y, Left, Left, Right, Left, Right - Level 5
A,B,X,B,A,B,B,B+L - Snot A Problem
Y,X,Y,X,A,B,A,X - What the Heck
A,B,Up+Y,Up+Y,Left,Right,Left,Right - Who Turned out the Light?

Cheat Codes:
Pause the game before entering these codes:

Y + X, B, Y, B, X, B, X, X - Extra continue
A, X, A, X, A, A, A, A - Map View Mode
B+X, B, B, B, A, A, X, A - Extra life (infinite use)
A, B, X, Y, Y, X, B, A - One-time (per stage) energy refill
A+X, B, A, B, X, X, X, X - Infinite energy refills
A+Left, B, X, A, A, B, X, A - Debug menu
B, B, A, X+Y, B, A, A, A - Extra life (once per stage)
A,B,X,A,A+X,B+X,B+X,X+A - Level Skip (Alt.)
Y,A,B,B,A,Y,A,B - Nick Jones Code
A+X,B,B,A,A,X,B,L+R - Plasma Power Up (Infinite Times)
A,A, B+L,A,A,X,B+L,X - Plasma Power Up (Once per stage)
A, B, A, B, X, Y, X, Y - One time only extra continue
A+X, B, A, B, X, X, X, X - Ammo refill
Select, B, X, A, A, X, B and Select - Level Skip

Strange Death:
This is a very simple code, but it's kind of funny. When you are at the Buttville stage where you must use the helicopter head to fly downwards: There are two different paths to take in order to complete the stage. Take the left one, but don't leave yet, just stand on the ground near the exit. Now, run into the thorns until Jims health reaches from 20% to 30%. Now when you get hit this time- the second you get hit, run to the exit where you get warped to the next stage and Jim won't be dead yet. You'll appear in the next stage,now quickly run as soon as the stage begins, and it looks like Jim has a heart attack or something because he dies for no reason- this is most likely because the game couldn't calculate the damage taken by the thorns fast enough to make Jim die in the previous stage.