During gameplay and when controlling Shaggy, hold L and press C-Up, C-Down, C-Up, C-Down, Up, Down, Up, Down, Right, Left, Right, Left.
Infinite Courage
During gameplay and when controlling Shaggy, hold L and press C-Up, C-Left, C-Down, C-Up, C-Down, Up, Right, Down, Left, Up, Left, Down, Right, Up, Down.