Go to the main menu and press L, L, R, R, L, R, L, R
Go to the main menu and press L, L, X, X, Y, X, L, R
At the Plant Electrocution Level 2 slide down toward the holes in the ground and go in the 2nd hole. Make sure to glide into the hole and glide toward the lighted area. Pick up the items (key). Get the grapple and use it to get out of the hole and finish your slide. The key you got was for the door beside the vines behind the glass. Now go in and fight the plant man and get a envelope that has a 'C' on it. When you finish the game this will activate the cheats.
Go to the main menu and press Y, X, Y, X, L, R, L, R
Go to the main menu and press L, R, Y, X
Go to the main menu and press L, R, L, R, X, X, Y, Y
Go to Plant Electrocution 2. When you get to the part where you see Mayor Hill, sneak around him until get to the door go through the door and you will not have to fight Trench Coat. You will only have to fight Poison Ivy's greatest creation.
Go to the main menu and press X, Y, X, Y, L, R, R, L, L