After beating Treasure Trove Cove, go back to Banjo's House, outside Gruntilda's Lair. Once inside, look at the 'Bottles The Mole' picture and you will go into a secret game of 'Put the Moving Puzzle Together.' Once all the pieces are fitted, congratulations! You've just accessed the first code. To redeem it, go to Treasure Trove Cove, drain the water around the castle, and enter. Every time you complete one of his puzzles he will give you a new code, they are as follows...

BOTTLESBONUSONE - Gives Banjo Big Head
BOTTLESBONUSTWO - Gives Banjo Big Arms and Legs
BOTTLESBONUSTHREE - Gives Kazooie Big Head
BOTTLESBONUSFOUR - Gives Banjo a Skinny body and a Little head
BOTTLESBONUSFIVE - Gives Banjo a Skinny body, Little head, Big hands, and Big feet.
BIGBOTTLESBONUS - Gives Banjo a Skinny body, Big head, Big hands, Big feet.
WISHYWASHYBANJO - Turns Banjo into a washing machine.

NOTE: To cancel these codes, enter the code NOBONUS