Without contest George is the most deceptive and secretive character of Seinfeld.  His secretive behavior is at large because of his frugal and miserly personality.  George is promoted as cheap by the rest of the characters.  In one episode George asks " to know the truth". Elaine tells him he is cheap.  George is hurt by this  accusation by such a close friend.  However, the comment is precisely correct, George is extremely cheap and expresses this quality countless times in the episodes.