Each of these codes are used on the world map screen.

Bonus Challenge - "Left, L, Right, R, Up, Down, Select" Upchuck - "A, Left, Y, Right, X, Up, B, Down, Select" Ultra Ben Skin - "Up, Right, Down, Left, A, B, Select" Gwen 10 Skin - "Left, Right, Left, Right, L, R, Select" Galactic Enforcer Skin - "A, B, X, Y, L, R, Select"

If you enter a new skin, that is the one that will be active when you enter a level. Also, you will need to reenter a skin code when after you reload the game, otherwise you will have the default skin.

Each code will give you 1 extra point on your file (you will not earn 1 point per level on the Bonus Challenge, which is unlike every other one)