You ask it on WikiAnswers like you did, and you get an answer. The code is Spongestar, but you have to get all twelve bonus cards before you can unlock the secret chracter
The secret character code in SpongeBob Monopoly is "SpongeStar" but you do have to achieve all of the bonus cards.
Monopoly Spongebob SquarepantsEdition unlock all the bonus card then, it will show you the code.
The code is spongestar, but you have to get all twelve bonus cards to unlock the secret character
cher
spongestar
BlackJack.
dont listen to him
WAVE
Booty
meyou
Isn't it the Plankton Coin thing? I could be wrong.
booty is the code